I've found the winning formula to enjoy any movie you see, and it's all about expectations.
I'll start by saying that you should always wait to see a movie, like a week or two. The only time this rule does not apply is if you know you will love the movie. This way you can hear about the movie, from friends, colleagues or reviews. After hearing enough about it you'll form an expectation. If you hear that it's crappy but you still want to see it, expect it to be bad, that way you might be surprised. I've recently done this with Fast & Furious and Terminator Salvation.
There will be times when you'll hear it's good and you hate it, or you'll hear it's bad and and you still think it's bad. I heard that X-Men Origins: Wolverine was a really good movie, so I went to see it. It was the most god awful crap I've seen in a long time, maybe ever. Saying that, this formula for enjoying movies does not have a 100% success rate, but it's close.
This formula should work for other forms of media as well, like books, video games, or TV shows (if you're willing to buy the DVD or download them). I'd imagine the rules will be somewhat different with these but the general concept is the same. So remember, be patient and wait to see/buy, find out what other people are saying, set an expectation, and enjoy (hopefully).