Would Rushmore count a romantic comedy? it focuses on a (twisted) love triangle and is damn funny

Nice list all the same.

Down With Love – It's so artificial, and yet that artificiality is its entire point, acknowledging that the battle of the sexes is a silly facade. And Zellweger and McGregor (and Hyde Pierce and Paulson) have NEVER been better. And I can't help but wonder if Pierce and Paulson were deliberately cast, as Pierce is out gay and Paulson is out lesbian.
Music and Lyrics – Okay, so it's not directed with much flair or anything other than plain competence. That aside, Hugh Grant and Drew Barrymore just WORK. And if nothing else, the music is fucking amazing. I still listen to Pop! Goes My Heart and Way Back into Love all the time.
Punch-Drunk Love – Well, duh. I don't know what I can say here that hasn't been said elsewhere, but a film that manages to turn Sandler's manchild instincts into a source of strength rather than a crippling flaw is impressive. Also, it's kind of a super-hero film. Or an alien film. Kind of open to interpretation.
WALL-E – Okay, so it's also an animated science fiction film. But the core story is about a lonely janitor who meets a dream girl and then EARNS her love the hard way, following her across the galaxy and beating his programming just to fulfill HER objective. Okay, granted, you could take it as the ultimate Internet Nice Guy story, but I choose not to, okay?
Ninotchka – God, I wish Garbo had been a comedy star. Knowing this is her only major comedy role is DEVASTATING, because she takes to it like a fish in water. Or like a conservative politician at an NRA meeting. Well, you get the idea.
Raising Arizona – Because romantic comedies don't have to be about meet-cutes. Some of the best are about husbands and wives falling back into love with each other, or renewing their commitment, or proving themselves to each other. And I can't think of many screen couples I wanted to succeed while watching the film more than Hi and Ed.
Adam's Rib – Another terrific dissection of the BATTLE OF THE SEXES. Spencer Tracy was always sort of manly, but he tended to be best at playing deeply empathetic characters with a more feminine sense of understanding for his fellow man, and so his match with Hepburn is screen bliss, a hard-driving woman and a sympathetic man, each testing at the boundaries of their gender while at each other's throats.
What's Up, Doc? – because before seeing this movie, I hated Barbra Streisand. And now I can't. Also because Ryan O'Neal is a seriously underrated actor (or he was just used well in three masterpieces: Doc, Paper Moon, and Barry Lyndon). And that chase down the streets of San Francisco is pure madcap bliss.
Moonstruck – I guess I'd have to say Nic Cage was never better than as a goofy romantic figure. I mean, I know it's cheesy and maybe full of stereotypes, but every actor brings these stereotypes into the realm of living, breathing humans. Not just Cage and the divine Cher, but Dukakis, Gardenia, Mahoney, Aiello, and the rest.