Some movies are complex stews: They taste richer the second time around when all the flavors reveal themselves. I find this most true with comedy and mystery. In funny movies I'm laughing so hard I don't catch all the jokes the first time around. In mysteries, on repeat viewing I see how and where the filmmakers have seeded the story. It wasn't until the third time I saw The Godfather that I could tell Tessio from Clemenza.
Recently Amy B asked for movies that fit the "Once is Not Enough" rule: Here is a provisional list, to which I'd add most screwball comedies and movies with fractured narratives and surprise endings. Just as certain music grows on you, so do these films.
All About My Mother; Angry Harvest; Babe; La Belle et La Bete; Blow Up; Bottle Rocket; Cache; Casablanca; Chinatown; Clueless; Contempt; The Conversation; The Crowd; The Departed; E.T.: The Extraterrestial; A Face In the Crowd; Femme Fatale; The Godfather (I & II); Groundhog Day; Howards End; I Know Where I'm Going!; It's a Wonderful Life; Jerry Maguire; La Avventura; The Lady Eve; Laurence of Arabia; Lost in Translation; Malcolm X; Michael Clayton; Modern Times; The Man Who Would Be King; North By Northwest; Notorious; On the Waterfront; Ordet; Raging Bull; The Rules of the Game; The Searchers; Shadow of a Doubt; Sherlock, Jr.; Some Like it Hot; Something New; Spartacus; Spirited Away; Sweet Smell of Success; Swing Time; Syriana; Tokyo Story; Toy Story 2; 2001: A Space Odyssey; Singing in the Rain; The Sixth Sense; Training Day; Vagabond; Vertigo; The Wild Child The Wizard of Oz.