X-Men 2, Spider-man 2 and you could make a case for Superman II and Blade 2 (which contains a scene where a vampire suplexes a guy through the floor) as better than the first movies in their series. So there may be a special case for comic book-inspired movies.
Also, Grease 2 smokes Grease. All good-hearted people know this.
I'm not sure if Wayne's World 2 is better, but I like the cases being made and I think I could come over to that side. It might be the most unexpectedly good sequel.