Depends on the film. I prefer to see opening credits in most films though, especially if done in a lovely creative way. But if it's just boring white font over a black background appearing in the same part of the screen for minutes, I'd rather it was just a title and that's it, or the credits play over the starting footage.
I've noticed that Nolan's most recent films (The Dark Knight and Inception) have no opening credits and don't even show the title until the end of the film.
I like credits that play over bird eye travel shots:
Crimson Rivers is one I like, the music helps by a fantastic composer. I can't seem to find a video for the opening of the sequel though, that's one I adore too:
I hate opening credits, but the credits for Fight Club were cool.
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Best Opening Credits of all Time.
Comic, Funny, Silly, Fun, Animated, and best of all an AWESOME score!
As for titles and credits till the end of the film is not something someone invented new. Sergio Leone was pretty good with Duck, You Sucker and Once Upon a Time in the West.
I wouldn't say opening credits are essential, but when they are done well they really do add something to the film. Its enjoyable when they stretch their legs creatively when making the opening credits. Although like others have said, bland opening credits can be gone without IMO.