Movies that you thought would be bad, but turned out great

I remember the first time I saw Pee-Wee's Big Adventure at someone's home. Their kid watched his TV show on a regular basis, so they planned to watch the movie when it showed up on cable. I resigned myself to watching it with them, only to discover that it was really a lot of fun, and also a clever homage to classic films. It turned out to be one of my favorite re-watchable films.