Hellboy 2:The Golden Army, Get Smart, Kung Fu Panda were very popular movies with my Middle School students.
Like everyone who's mentioned Kung Fu Panda most of my middle school students complained because they had seen it, but they still preferred it over doing any kind of classwork. I liked using Kung Fu Panda because I was able to find a lot of activities for it.
Originally Get Smart wasn't popular because they never heard of it so they didn't want to see it, but after I told them they could watch this or do classwork, they decided to watch the movie. And...they absolutely loved it. They were always laughing and even my co-teachers thought the movie was entertaining. Also if your students are into pro wrestling they might like it because of The Great Khali and The Rock who play big roles in the film.
Hellboy 2 was more popular with the boys than it was with the girls. My guess is that most of them have seen it too many times by now also.