Thinking of PERFECT movies --- the ones that you can see over and over again and they never lose their punch, even when you know them by heart, and you wouldn't change a thing. Most of the ones on my list are comedies, but not all. In no particular order:
Singing in the Rain, The Best Years of Our Lives, Ruggles of Red Gap, Kind Hearts and Coronets, Some Like It Hot, Fail Safe, In Which We Serve, The General, Mrs. Miniver, The Lady Eve, The Maltese Falcon, Stagecoach, Lost Horizon, King Solomon's Mines, Limelight, Ninotchka, I Married a Witch, Dr. Strangelove, Grand Illusion, I'm No Angel, Captain Blood, A Midsummer Night's Dream (1935), Random Harvest, Ghostbusters, A Hard Day's Night.
This leaves out a lot of movies I love -- Zulu, for instance, is one I always enjoy watching but has an irritating and completely unnecessary subplot with an idiotic missionary girl. Goodness knows I love Fred Astaire, but nearly all of his movies have irritating subplots. Many favorite stars and directors don't make my list because of weak supporting players or silly plotlines. The same with musicals -- I love musicals, but how many are there where you wouldn't change a thing?
But the little moments from the perfect list that I know by heart -- Effie Floud forgetting herself and sympathizing with Ruggles hangover, Some Like It Hot's all too confident bellboy, Eugene Pallette trying to achieve some breakfast in the Lady Eve, Mae on the phone in I'm No Angel "Juror Number Six? Of course I remember you, you were the one with the nice, kind face", Joe E. Brown as Thisbe in A Midsummer Night's Dream -- get even better with age.