The two fiances in Corpse Bride fit this trope—shy, proper, living Victoria is the Betty and the lively-but-dead Emily is the Veronica. Except that Victor specifically wants to marry Victoria; Emily was in the picture thanks to a rather weird Accidental Engagement. Victor eventually ALSO wants to marry Emily; but, knowing that doing so would kill him and would make Victoria as sad as she is herself without any chance of closure, she rejects him at the last moment.
Disney's Pocahontas also genderswaps this with Kocoum as the Betty and John Smith as the Veronica, although the contest clearly ends when Kocoum dies.
Though this is also somewhat subverted as Pocohontas isn't torn between the two, she clearly doesn't want to marry Kocoum, it's more of a choice between her fathers's wishes and her own desires.
The sequel adds John Rolfe as a new Betty, though John Smith is largely absent anyway. In the end, Pocahontas follows the history books in winding up with John Rolfe.
Robots has Piper (Betty) and Cappy (Veronica), but their personalities are switched. Rodney (Archie) chooses Cappy, and he is unaware of Piper's affections. However, the two girls get along well.
The Cincinnati Kid has a textbook Betty and Veronica love triangle, so much that the 2nd paragraph of this page sounds like it's describing this movie. Steve McQueen is the hero, a poker player dating Tuesday Weld (Betty) who is pretty, sweet, and kind of dull, but he's drawn to the wild and sexy Ann-Margret (Veronica), who is married to a friend of his but constantly flirts with him. True to form, Weld is a blonde and Margret is a redhead.
A "color-coded" triangle exists in film noirs The Postman Always Rings Twice 1946, Tension, and Out of the Past (where the evil Veronica, Jane Greer, dresses all in white, as Lana Turner had in "Postman"). In the black and white film Dark Passage, both the Veronica and Betty characters (Agnes Moorhead and Lauren Bacall respectively) are brunettes, but Moorhead's character loves and is coded by the color orange.
This was a popular trope in Film Noir. Other examples include:
The Maltese Falcon - Effie Perine is the Betty and Brigid O'Shaughnessy is the Veronica, with Sam Spade as Archie
Double Indemnity - Lola Dietrichson is the Betty and Phyliss Dietrichson is the Veronica, with Walter Neff as Archie
Laura - Both Diane Redfern and Anne Tredwell are Bettys to Laura Hunt's Veronica and Shelby Carpenter's Archie
Murder, My Sweet - Anne Grayle is the Betty, Helen Grayle is the Veronica and Philip Marlowe is Archie
Detour - Although not really a love triangle, Sue is a Betty, Vera is a Veronica, and Al is the Archie
Mildred Pierce - Mildred is the Betty, Veda is the Veronica, and Monte is the Archie
Leave her to Heaven - Ruth is the Betty, Ellen is the Veronica and Richard is the Archie
The Big Sleep - Vivian is the Betty, and Carmen is the Veronica to Philip Marlowe's archie
The Killers - Lily is the Veronica, Kitty is the Archie, and Ole Anderson is the Archie
The Strange Love of Martha Ivers - Tony is the Betty, Sam is Archie and Martha is the Veronica
Sunset Boulevard - Betty is, well, the Betty, Norma is the Veronica, and Joe is the Archie
John Hughes has used this binary triangle with some success. In Pretty in Pink, the traditional "Betty/Veronica" triangle exists between two boys and a girl (Blaine, Ducky, red-headed Andi)... Yet the unpleasant "Reggie" archetype is played by the blonde, wealthy James Spader, who seeks to sabotage his friend Blaine, an "Archie" type nice boy. The character of Duckie is comic relief, like "Jughead," but unique in that he's also a love interest. Pretty in Pink was originally shot to have her end up with the Betty (Ducky) as well, but thanks to Executive Meddling, that didn't happen.
Hughes also played this trope straight in Some Kind of Wonderful - a red-haired "Archie" (Eric Stoltz) loves a popular girl (Lea Thompson) with brown hair, but can't see that his blonde best friend (Mary Stuart Masterson) loves him.
This was also used in Sixteen Candles, when the male love interest is dating the blond cheerleader (Veronica) but spends most of the movie trying to hook up with the red-headed plain but not-superficial girl (Betty). The cheerleader gets this herself, when she leaves said male love interest (Veronica) for a geeky but sweet kid she went home with while drunk (Betty). And since that geeky kid had a crush on the plain red head, he himself chose the Veronica over the Betty.
The Mask: The Betty, a news reporter, sells Stanley out to the Big Bad, while the Veronica, the Big Bad's Moll, is the one who stays true and ends up with him.
A Cinderella Story: Football-quarterback-and-closet-poet Austin Ames has the choice between his bitchy ex-girlfriend Shelby Cummings or Sam Montgomery, this mysterious girl he's been writing on the internet. At the beginning you could say Shelby is the Betty because she knows Austin very well and hangs out iwth him and his popular friends, and Sam would be the Veronica because she is his mystery "dream girl." But after he finds out who "Cinderella" is, Sam is his down-to-earth, shy Betty and Shelby is his cunning, mean-spirited Veronica.
How To Lose Friends And Alienate People: Protagonist Sidney has to choose between sensible and earnest coworker Alison and seductive yet vapid starlet Sophie Maes. Alison, meanwhile, has her own Betty and Veronica scenario - with Sidney as the Betty and Sidney's boss Lawrence Maddox as the Veronica.
Featured but skewed in Strange Days, where the Betty is an ass-kicking tough-as-nails limo driver who is devoted to the (slightly skeevy) main character, and the Veronica is a flaky, self-centred punk rock singer who broke the main character's heart and who he's been obsessed with ever since. The Betty wins out, mainly because the Veronica slept with the main character's best friend and conspired with him to frame the main character for two murders.
In Mormon movie The Single's Ward the protagonist dumps the non-Mormon Veronica for the Mormon Betty after he has an epiphany and realizes that he values his faith.
Terrence Malick's The New World applies this trope to the story of Pocahontas, who has to choose between John Smith (Veronica) and John Rolfe (Betty).
In Teen Wolf, the main character Scott Howard lusts after the blonde cheerleader Pamela, while ignoring his Hollywood Homely female best friend Boof (who is in love with him). When he becomes popular, he has sex with Pamela. In the end he becomes involved with Boof.
Also gender-flipped in Pirates of the Caribbean with Jack as the Veronica and Will as the Betty. Elizabeth must choose between them...not that there's ever much doubt about who she'll choose, seeing that she's been in love with Will from the beginning and never shows much interest in Jack. But still, the option was there (and fans in particular liked to explore it).
Slight variation in that neither of them was the man her father would have preferred her to marry, giving her a Third-Option Love Interest on James Norrington, a suitor from her own social class. Will takes the Betty role by being a slightly less bad choice, as at least he's well-behaved. Usually.
Where Betty acts as antagonist and Veronica a protagonist, in Titanic, Rose is expected by her mother to marry the rich Cal Hockley (Betty), but instead comes across Jack Dawson (Veronica).
In Death Becomes Her, Helen, a shy, timid Betty in the beginning of the movie, is desperately afraid her fiance Ernest will fall for Madeline, her childhood friend, who is a flashy actress and definite Veronica. Depending on how you define the roles, though, they become less distinct after the first fifteen minutes of the movie.
This trope is a favourite for David Lynch, although he never plays it straight.
Mulholland Dr.: Betty is, well, "Betty", and Rita is "Veronica". Initially subverted in that, instead of being two sides of a love triangle, they initially develop a lesbian relationship. It gets more complicated later on. One might even argue that Rita is the Archie and Adam is the Veronica.
Blue Velvet has Jeffrey torn between the blonde girl-next-door type Sandy and the mysterious, tortured Broken Bird Dorothy.
Twin Peaks sets up the wholesome Donna Hayward as the Betty, in contrast to rich bad girl Audrey Horne. The twist is that Audrey turns out to be probably the better person of the two, with her plot arc serving as a deconstruction of how Veronica-type characters are usually "punished" in stories. Audrey puts herself in danger to try to solve the murder. Donna puts other people in danger, and eventually drives an innocent man to suicide.
Played very weirdly, much like everything else of course, in Eraserhead, where Henry cheats on (or perhaps, only fantasizes about cheating on?) his frail, weepy wife, Mary, with the mysterious, nameless Beautiful Girl Across the Corridor.
In Caveman, Atouk lusts after the sexy but shallow Lana. When she becomes interested in him, he rejects her for his friend Tala.
The plot of Two Lovers, although the brunette is the stable one while the blonde is wild. Another exception in the brunette and blonde appearing to be of equal attractiveness.
Star Wars. With Princess Leia Organa herself as the Archie, good-hearted, loyal, and friendly farmboy/Jedi Luke Skywalker is the Betty. Roguish, rough, and experienced Han Solo is the Veronica. Rather luckily (given the later revelation that she was Luke's Long Lost Sibling), she chose Han.
Inverted in Forgetting Sarah Marshall, where the protagonist chases after the wholesome, apple-pie blonde all-American girl and ends up with the wild, exotic boob-flashing brunette from Hawaii.
Subverted in Not Another Teen Movie, where Janey, having to choose between Jake (The Jock who dates her only because of a bet with his Jerk Jock buddy) and Ricky (the annoying, whiny loser of a "friend"), chooses the former, causing him to have a change of heart, while the latter remains an annoying whiny loser.
The movie adaptation of The Phantom has Diana, Kit's ex-girlfriend, and Sala, the female leader of a gang of Air Pirates.
Cat People has the male lead falling for the beautiful, exotic, Serbian Irena, but later leaving her for his sweet, dependable, American coworker Alice. (Partly because Irena wouldn't sleep with him.)
A genderswapped version with Enkil as the Betty and Lestat as the Veronica to Akasha's Archie. Lestat most decidedly wins when Akasha murders Enkil in order to pursue Lestat. And then...
Akasha as the Veronica and Jesse as the Betty to Lestat's Archie. Jesse wins when Lestat turns on Akasha in order to save his Betty.
Bram Stoker's Dracula has (although Bram Stoker's Dracula does not) a genderswapped version with Mina as Archie, Dracula as Veronica and her much more average fiance Jonathan as Betty. Dracula dies, but it is not made entirely certain that Mina goes back to Jonathan.
On the other hand, one could view Mina as the Betty and Lucy as the Veronica to 'The Man Himself'. As it's a matter of Death rather than love, and Dracula does try for both, this is probably a subversion (or even just a nod to the trope rather than an instance proper.)
Made Of Honour is built on this. The story revolves around lead character Tom (Betty) falling in love with best friend Hannah (Archie) and stopping her wedding to ultra-perfect, royal Duke, Colin (Veronica).
In The Age Of Innocence, Newland Archer is engaged and eventually married to May Welland, a lovely but completely ordinary socialite (The Betty), while falling in love with her cousin Ellen, the family reprobate (The Veronica). This trope is played even stronger in the book, where May is blond and blue-eyed and Ellen dark-haired. Subverted somewhat in that in this case, the Betty is wrong for him, despite their similar backgrounds and upbringing.
The 2010 Rupert Grint movie Cherrybomb has another genderswapped version, with Michelle as the Archie, having to choose between the (relatively) safe and dependable Malachy (Betty) and the rebellious, dashing Luke (Veronica).
In Vicky Cristina Barcelona, the blonde Cristina (Betty) and the brunette (Vicky) are involved in a love triangle with Javier Bardem's character.
The Deaths of Ian Stone sets up the protagonist with a sweet-natured blonde Betty, then shifts him to dating an increasingly unnerving dark-haired Veronica as the Dream Within a Dream kicks in. Neither he nor the Veronica are even remotely human, and he loved her before abandoning her for the Betty who by all rights should have been his prey. The plot of the film is based in her attempts first to snap him out of it, then to get revenge.
Spider-Man 3 reverses the comics' version of the characters, casting Gwen Stacy as the Veronica and Mary Jane Watson as the Betty to Peter Parker's Archie. Peter eventually chooses Gwen while under the influence of the Venom symbiote, but manages to offend and alienate both of them with how much of a douche he's become.
In Clerks, Dante Hicks is dating Veronica (Betty) when an old flame from high school comes back into his life, Caitlin Bree (Veronica). Veronica brings him lasagna at work and is trying to get Dante back in school. Caitlin is engaged (but calls off the wedding), and cheated on Dante in high school. He winds up trying to go for Caitlin, and losing them both. Veronica dumps him, and Caitlin goes catatonic after screwing a random dead guy in the Quick-E-Stop's restroom, thinking it was Dante.
In Clerks II, Dante has another choice between his high-maintenance fiancee Emma (Veronica) and his boss, Becky (Betty). This time he actually gets the girl and ends up with Becky.
While the two female love interests in Cassandra's Dream aren't part of a love triangle, each being involved with one of the two brothers, their personalities fit perfectly the trope: Kate is the soft, reasonable girl next door, and Angela the sexy, intellectual actress.
Sweeney Todd: The Demon Barber of Fleet Street somewhat deconstructs the plot with the Johanna love triangle. To the audience it's very clear that Anthony (nice guy her own age) is Betty and Turpin (ruthless old pervert who raped her mother) is Veronica. However Turpin sees himself as a responsible gentleman Betty attempting to "shield Johanna from the evils of the world" by fending off a lustful young Veronica.
Wallace and Victor Quartermaine in Wallace & Gromit: The Curse of the Were-Rabbit.
She's Out of My League plays around with this. For Molly, Kirk is the Adorkable Betty and Cam, her ex-boyfriend, is the Veronica. Meanwhile for Kirk, the beautiful and worldly Molly initially seems the Veronica and his familiar ex-girlfriend Marnie is the Betty. However Molly is genuinely nice and Marnie is not.
The 1927 silent film It (not to be confused with Stephen King's IT) has reserved, aristocratic blonde Adela (the Betty) and sexy, fun-loving working class brunette Betty (the ironically-named Veronica) vying for Cyrus's affections. As Betty is the titular "it" girl and Cyrus is clearly attracted to her (even when he doesn't want to be) and oblivious of Adela's feelings for him throughout the entire film, it should be obvious which girl wins in the end.
The Olsen twins. Everything that they've ever been in. Ashley's character might be interested in fashion and modeling or be the cool surfer chick but will always be the boy-crazy Veronica while Mary-Kate's character might be a serious student or serious athlete but always the down to earth one.
Something New: Mark (Betty) and Brian (Veronica) for Kenya (Archie). Mark has no cultural or color divide to overcome and works a similar professional job and comes from an acceptable social status. Brian does not.
In a deleted scene from Pulp Fiction, Mia Wallace runs a personality/pop culture test on Vincent Vega. One of the questions is "Betty or Veronica", and Vincent chooses Betty, claiming never having gotten Veronica's appeal. Which is made interesting by the fact that Mia is a total Veronica.
The 1945 French classic Children of Paradise. Amid its Love Dodecahedron is the triangle between the mime Baptiste, the sultry carnival performer Garance (Veronica) and Nathalie (Betty), daughter of the manager of the theater where Baptiste is a star. In a variation on the usual formula, Garance loves Baptiste, but his shyness and her many other suitors stand in the way of their romance (also, both women are brunettes). Eventually Baptiste marries Nathalie, only to have Garance re-enter his life.
In the 1993 ski film Aspen Extreme, one of the main protagonists, TJ Burke, is involved in a love triangle between two very different women: a down-to-earth and beautiful radio DJ named Robin Hand (the Betty) and a seductive millionaire businesswoman named Bryce Kellogg (the Veronica).
A variant appeared in The Captain's Paradise, where Alec Guinness was married to quiet homebody Maud (Betty) but had the sexy and vibrant Nita (Veronica) as his wife in another port. Hilarity began ensuing when he mixed up his presents for them, making Maud ecstatic that he saw her as physically desirable and Nita thrilled that he was willing to acknowledge her domestic side.
Subverted in The Dark Knight Rises. Bruce Wayne/Batman is attracted to both Miranda Tate (CEO of Wayne Enterprises, as well as a prim and proper society lady) and Selina Kyle (Catwoman)...but Miranda turns out to be Bane's Man Behind the Man and the film's Big Bad, who wants to nuke Gotham.
In Dangerous Beauty, Marco Venier is caught in a love triangle between his dutiful, God-fearing, obedient wife, Giulia de Lezze, obviously the Betty, and the sensuous, promiscuous, dangerous courtesan Veronica Franco, who is, well, the Veronica. Interestingly, Veronica was very much a Betty herself, and she and Marco were in love in their youth, and wanted to marry, except that Veronica's family had no money for a dowry, forcing her to become a courtesan in order to support herself. The film in general has much more sympathy for Veronica, who is, after all, the title character, protagonist, and heroine, than for Giulia, whose only faults are that she is not as sexually adventurous as a courtesan, and that she resents the fact that her husband openly patronizes a courtesan.
In the backstory to It's a Wonderful Life, young George Bailey has to choose between Fille Fatale Violet and wholesome Mary — naturally, he picks Mary. Later in life there are vicious rumours about the fact that George and Violet are seen having private conversations (gasp!), though really he's just helping her out financially.
In The Legend of Frenchie King, the bumbling sheriff is attracted to the leads Marie Sarrazin and Louise King. Marie is the Betty, being the one the sheriff has known for longer and therefore more approachable, and the mysterious (outlaw) Louise is the Veronica. He wins neither. They seem more interested in each other than in him at any rate.