In Buffy the Vampire Slayer Faith envies Buffy for being the "main" slayer, having friends, family, love, acceptance, etc. So she envies Buffy's life in general — right until she has to lead the charge.
In both Buffy the Vampire Slayer and its spin-off Angel, Angel has been shown quite frequently, despite having left her for her sake, been openly jealous towards Buffy's love interests or suitors, especially to Riley and Spike. So has Spike; the episode "The Girl In Question" has them try to find her when they find out she was dating their former rival, their excuse being they were worried about her.
The brotherly relationship between Frasier and Niles Crane is dominated by this trope.
Farscape had an episode actually called Green-Eyed Monster, in which Crais' jealousy of Crichton (and vice-versa) nearly led to Crichton's death. It also led to John telling Aeryn about his feelings, again. To be fair, the near death was courtesy of Talyn, not Crais. He actually had him Thrown Out the Airlock.
Oh come on, Talyn gets all his ideas and feelings from Crais, pretty much. He's just a very powerful baby who wanted his Mummy and Daddy to stay together - though, admittedly, the fake sex tape of Crais and Aeryn isn't something most toddlers would come up with.
Friends: Ross towards Paolo. Chandler towards Richard as he believes for a long time that he's still the love of Monica's life and is sophisticated, mature, an eye doctor and and able to grow a moustache. After they're married Monica points out how silly this is given she chose him over Richard several times. As an Insecure Love Interest he has trouble acknowledging this. Also worth remembering that all his previous girlfriends cheated on him, so his fears aren't exactly foundless.
Rachel and Phoebe are also this towards Monica and Chandler relationship, as they're depressed about not having anyone themselves. Lampshaded in Season 6 when Chandler's planning to propose and they say they're only 2% jealous...then 10%...then 20%...
Ross is this repeatedly. When they begin dating, he is extremely jealous of Rachel's colleague Mark, despite the fact that Rachel shows no romantic interest in him. He is also jealous of Emily's burgeoning friendship with Susan (Carol's lesbian lover), believing she will steal Emily from him. Monica points out that his divorce from Carol must have really done a number on Ross since in high school, Ross was not a jealous person despite the fact that ALL of his girlfriends were cheating on him.
In Desperate Housewives episode Back in Business, Mary Alice's ending narration focuses on the various types of envy, stating that if you look carefully at the people near you, you may spot a green-eyed monster.
iCarly: Freddie suffers this in iLike Jake and iDate A Bad Boy. Carly also gets this like whoa during the recut version of iSaved Your Life. When a slutty girl comes up to Freddie and offers him weekend sex with her whilst her parents and brothers are away, Carly grabs Freddie by the shoulder, embraces him and starts French kissing him so the girl will take the hint that Freddie is taken, much to his surprise (and approval).
In Robin Hood, Guy of Gisborne envied Robin his popularity and status as a national hero, and the love of Marian.
In the third season, Kate envied Isabella and Guy because of Robin's continual obsession with all things Gisborne-related.
An episode of Hercules: The Legendary Journeys had Cupid turn into a literal green-eyed monster when the woman he was in love with fell in love with Hercules (who reciprocated due to being struck with one of Cupid's arrows).
Prince Arthur a couple of times on Merlin. He responds to the sight of Lancelot and Guinevere holding hands by throwing a Big Sulk (and this is before he and Guinevere are in a relationship), and later gets riled at Gwaine for flirting with her. The fact that both knights have been reinstated at Camelot gives you the feeling that this is heading somewhere...
One of the longest running jokes in Everybody Loves Raymond is how much Robert envies his brother, Raymond. In his rants, he would talk about how "Everybody loves Raymond", how his mother favors Ray over him, how much successful Ray is compared to him, and how he has a better life than him(at least in his eyes). It gets to the point that when ever Ray fails at something or doens't get what he wants, Robert would find joy in this and openly mock him for his shortcomings.
Mash has Margaret, who is jealous of Frank's wife. When she finds out Frank bought a set of expensive pearls for his wife and a second, cheaper set for her, Margaret devises a plan to get Frank to swap out the cheaper ones so she will have the more expensive necklace and Frank's wife will get the cheaper set.
The tables get turned when Margaret marries Donald Penobscot. Frank's own jealousy causes him to kind of lose his marbles and he ends up sent back to America on a Section 8.
Lex: You were always one step ahead of me. Clark: It wasn't a competition. Lex: Of course it wasn't; you're simply better than the rest of us. Clark: And that always killed you, didn't it? Lex: No. What killed me was that you didn't evenwantit. You rejected it. If I had your destiny, I would have embraced it.
In the Castle episode "Eye of the Beholder", Castle and Detective Beckett are joined on their investigation by Serena Kaye, a classy, attractive insurance investigator who is clearly attracted to Castle and whom Castle begins to find intriguing in return. Not entirely surprisingly, Beckett spends most of the episode seething with badly-concealed jealousy about this.
In general, Beckett seems prone to struggling with her inner-teenager-with-a-case-of-this whenever other women attract Castle's attention.
On Leverage, Parker is this during the episode The Double Blind Job with regard to Hardison being friendly with the client. She later breaks a beer bottle as she is watching them talk.
This comes up periodically in Supernatural; people who don't know the boys see that they're handsome, tall, competent, charming, good liars, etc., and conclude they have it easy. As the stars of one of the most depressing shows on television, this is emphatically not true.
The loser behind the problem in the wishing well episode says something to the effect of them having it easy with their great looks and cool car, and they assure him in deadpan that they are absolutely miserable. This is a little surreal, in that it's true, but they say it like they're remarking on the weather. On the other hand, Sam lies to the asthmatic warlock kid in 'Swap Meat' that he'd love to have his life without the demon bounty hunters and blood addiction problems and responsibility for the Apocalypse and all that. Actually, he'll take all that rather than be that kid with the collegiate future locked in stone by his asshole family, and a no-good body. Probably the most significant factor being that by Season 5 Sam has long since grown uncomfortable with restrictions on his ability to kill the fuck out of his problems, and is not actually fit to live in society anymore, even if he is wearing a white hat again.
Played for Laughs in order to alleviate the high levels of tension in an otherwise rather grim and humourless episode of Sherlock (which is known - and loved - for its dry wit): John spends the entirety of A Scandal in Belgravia reveling in barely-concealed jealousy over how much attention Sherlock awards Irene, to the point where his Girl of the Week breaks up with him for being a better boyfriend to Sherlock than he is to her. John becomes completely incensed after the first time Irene fakes her own death, threatening her in an attempt to convince her to tell Sherlock that she's still alive. This doesn't stop him from feeling sorry about her apparent death at the end of the episode. Sherlock himself suffers from the Green-Eyed Monster whenever something other than the case they're working on distracts John.
In playing a conceited version of himself in Extras, Orlando Bloom seethes with jealousy over Johnny Depp:
MythQuest: In one episode, Cleo visits a Swahili fairy tale. The brother of the fairy tale's protagonist refuses to let her have any success, always claiming that whatever she earns belongs to him, despite how much wealth he alread has.
Surgical Spirit has Sheila, who used to date a coworker, got engaged to him but they then split up. Both of them start dating other people, but when the coworker's new girlfriend joins the hospital as a nurse, Sheila… isn't particularly kind to her for the first few days. She gets better, though.
On Once Upon a Time Zelena, the Wicked Witch of the West, physically turned green when she allowed her envy get the better of her. Once she gets over the fact that Rumpelstiltskin chose Regina over her, she returns to normal. Then she gets envious when Dorothy Gale turns up in Oz and is prophesied to be The Chosen, so she turns green again.