Bill and Ted might not be the best movie with time travel in it, but it has the best use of time travel in any movie I've seen.
The scene with them needing the keys, and decided to just use the time machine at a later point and get the keys and leave them right beside where they are now is brilliant. Having access to a time machine would pretty much solve most issues in a similar way, but unfortunately most movies ignore that (even Bill and Ted does, what with it's odd plot timer).
As far as the best movie, I vote Back to the Future.