I collect film credit sequences. Absolutely love them, and it's one of the reasons I dislike being late to the beginning of a film. To my way of thinking, if a director takes the effort to provide a memorable credits sequence for the film then it's safe to assume the rest of the film will be excellent.
(And yes, I've had my nose rubbed in that one. Don't joggle my elbow, pumpkins. Uncle Mikey's working.)
Titles for films are an art form in themselves, and people such as Maurice Binder, Saul Bass, Richard Williams and others have proven it again and again: often quietly working in background to establish a particular mood for the overall film.
What follows is by no means meant to be a "Best of" or complete list of excellent credit sequences, and doubtless some of you have personal favorites which you feel I should've included here. What I'm doing right now is providing the uninitiated with an idea of why he or she should get popcorn as rapidly as possible and find a seat before the theater lights go down.