The Castle: Darryl and Sal. She cooks, he buys things for the pool room. And they wouldn't have it any other way.
Spider-Man 2: Dr. Otto Octavius and his wife Rosie Octavius are not shown to have any marital problems or arguments and are portrayed as having a happy marriage.
The Thin Man: Nick and Nora Charles are always in lock step with each other throughout the film series. It's been said theirs was among the very first truly happy marriages depicted by American cinema.
Adam and Eve in Only Lovers Left Alive have been married for centuries. They're still desperately in love with each other, and that love forms the emotional core of the entire movie. Interestingly, at the beginning of the film they're not living together, implying that they occasionally spend long periods of time separated. Adam likens them to entangled particles, where they are both affected in the same ways even if separated to opposite sides of the universe.
Marge and Norm Gunderson in Fargo. When she's woken up in the middle of the night about a triple homicide, he wakes up alongside her, insisting that she at least needs to eat before heading off to work, so he makes her some eggs. Norm also brings her lunch at work. She brings him earthworms for his fishing and congratulates him for getting his painting on a stamp. At the end of the film, she states thoughtfully, "We're doin' pretty good."
Tom and Kate Baker in the 2003 Cheaper by the Dozen film and its sequel. They clearly love one another even after twenty-five years of marriage (twenty-three according to the first movie, plus the two that passed between films) and having twelve children. They argue a bit throughout the two films, but they ultimately make up, and are happy with each other.
All three main couples from the Meet the Parents series: Greg and Pam, Jack and Dina, and Bernie and Roz. Their conflicts are only with people outside their relationships.
George and Lorraine McFly were originally not happily married at the start of the series—him being a spineless loser in a dead-end job and her a depressed alcoholic who only married him out of pity—but after Marty's alterations to the timeline, Back to the Future ended with them charmingly in love with each other and their life. Given Lorraine's rant to Biff in the sequel, she and George had been happily married in that alternate universe before Biff had George murdered.
In the third movie, we see that Seamus and Maggie McFly were happily married as well despite the rough life they had on their farm. They were content with each other and their family, and did not see any need for pride or adventure to get in the way.
They may be dead, but that doesn't stop Adam and Barbara Maitland from being this in Beetlejuice. They're quite blissed out on each other, and a real contrast to the grating, saccharine Charles and Delia Deetz as well.
Alejandro and Elena in The Legend of Zorro for the most part. They do split up for awhile, but that was mostly because Elena was blackmailed into splitting up with him
The parents in A Christmas Story. Not even the legendary "Battle Of The Lamp" can permanently derail them.
Undercover Blues: Despite a few disagreements about, e.g., taking the baby into dangerous situations, Jane and Jefferson Blues are one of the finest examples of Happily Married to be spotted in an action film. Their easy camaraderie is an enjoyable counterpart to the danger they're facing.
Mike and Jackie Flaherty from Win Win. Their relationship can get harried, but it's ultimately a loving and commited one.
Donald and Tim in the Donald Strachey mysteries are this right from the start, and they're adorable. Not that they don't have their problems, particularly with Donald's dangerous and time-consuming line of work, but that's life.
Celia and Johnny in The Help. All Johnny wants from Celia is for her to be happy. He doesn't care that she can't cook, properly take care of their house or that she had multiple miscarriages trying to give him children. Their first scene together where Johnny sneaks behind Celia and pulls her in close establishes their relationship pretty well.
Greg Kinnear and his wife in The Matador are happily married, and their relationship is never at stake.
Andy Knightley from The World's End. Or so he claims. He's actually been having major difficulties as of late, although they get resolved by the apocalypse.
In The Brass Teapot John and Alice are truly happy together and very much in love, despite all their financial difficulties.
In Baghban all the couples in the movie, but Taken up to Eleven for Raj and Pooja. Even though they are married for 40 years, they behave like they are a young couple who are madly in love.
The Finest Hours: The epilogue shows that the marriage between Bernie and Miriam did happen on the planned date, and lasted for 58 years until he died in 2009.
In Suffragette the chemist and her husband have the only happy marriage shown in the entire movie. The husband is the only man shown who is supportive of women's voting rights, and the one time he's against one of her plans is when he's worried that she, due to her already damaged health, won't survive another run-in with the police.
In The Mummy Returns, which takes place nine years after the The Mummy, Rick and Evy are revealed to be married and have a son, Alex. Rick risks his life for his wife when he saves her from being killed by Imhotep and Anck-Su-Namun and she does the same when she runs toward him and saves him from being pulled into the Underworld as the temple crumbles.
Gomez and Morticia Addams, unquestionably so, in The Addams Family. Love at first sight, the pair regularly get Distracted by the Sexy even with guns pointed at them, and dance together every day. They even bid against each other in an auction as part of their romance, with escalating results. Summed up with this quote:
Gomez: "To live without you, only that would be torture."
Morticia: "A day alone, only that would be death."
The Old Man & the Gun: Detective Hunt is happily married to a supportive wife, and their relationship never causes any complications in the plot. Interestingly, it's a mixed-race marriage, which would have been more unusual in the Midwest during 1980s, but it's never even acknowledged.
Shelley and Helen Martin in Violent Saturday. Their marriage is used to contrast the rapidly disintegrating marriage of Shelley's workmate Boyd Fairchild and his wife.
All My Loved Ones: Jakub and Irma Silberstein are very happy together and they're loving, caring parents to Hedvika and David. Jakub is a successful medical doctor and his wife is at home, taking care of the house and the children. They also have loving relationships in their extended family, especially with Jakub's brothers.
Sappho: Sappho and Phil start out this way. Then things become difficult as Sappho grows enamored with a lovely woman on their vacation to Greene.
Miss Meadows: Mike and Miss Meadows (or Mrs.?) are shown as a very happy couple in the epilogue with their baby daughter.
In The Old Guard, the immortal fighters Joe and Nicky. They are not literally married — as their same-sex, inter-religious relationship would have been socially unacceptable for much of the time they've been alive — but they have been together for nine centuries and are still completely devoted, affectionate and even flirtatious with each other.
In Ring of Fear, trapeze stars Valarie and Armand St. Dennis are happily married: a fact that drives Dublin O'Malley, who is an old flame of Valerie, into a murderous rage.
Assault on Wall Street: Jim and Rosie clearly were deeply in love with each other. This makes it just all the more devastating when he's bankrupted by the crash then can't pay for her treatment. Rosie kills herself after realizing the burden she's become for him.
Ed and Lorraine Warren in The Conjuring Universe are still madly in love with each other after twenty-plus years, and while they have their share of arguments — usually about wanting the other to stay safe instead of running into danger — their love for each other never falters. Their relationship forms the emotional heart of the entire franchise.
Lorraine: I could go back to the house — but my home is here, with him.