For reference, the Internet Movie Data Base List. Interesting that nobody here has mentioned Casablanca. Great, but for me, not the definition of romance by any means.

I'd have to second It Happened One Night; I still haven't seen Bringing Up Baby.

Involving music: Little Voice and Hear My Song

Older folks: Nobody's Fool.

Older women: Bull Durham and While Palace

The sci-fi crowd: Groundhog Day and Late For Dinner (just noticed, but haven't seen Happy Accidents.)

John Candy: Only the Lonely and Delerious.

Someone mentioned The Thin Man as one of the few comedies involving a cheerfully romantic married couple. Can anyone else recall any really good movies along similar lines? I loved Tender Mercies, but it was more about perseverance and love than romance.

Arguments:
Truly Madly Deeply is superb, but the romance seems like a subplot compared with the grieving.
Local Hero is one of my top twenty favorite flicks, but I wouldn't call it a romance either.