Between Casablanca and Chinatown? That’s like choosing between my children. I’m going to go with Casablanca because so many lines - even misquoted - have ended up in popular use in the same way people quote Shakespeare and the Bible without realising. “Here’s looking at you kid”, “We’ll always have Paris”, “I think this is the beginning of a beautiful friendship”, “Round up the usual suspects”, “Play it Sam”, etc.