I grew up a comic book fan, falling in and out of the habit as I got older. The times in my life where I stopped reading comics didn't have too much to do with the comics themselves (although they probably did at times parallel a downturn in quality in the X-Men, the primary series I collected), but more to do with a lack of funds or my other entertainment options taking up my time. But then they started making movies about comics — more specifically, they started making GOOD movies about comics — and I decided to start reading comics again (albeit in much smaller doses).
So I write this list both as a fan of movies and a fan of comics. Thus, I'm also a big fan of movies based on comic books, when I'm not busy being a big critic of movies based on comics that fail to live up to the source material. This is a list I've been meaning to write for a few years now, and in that time, the list of candidates has only grown. Because the world of comic book adaptations has grown to encompass a nice variety of of genres and types, I felt a bigger list of 20 would lead to a more diverse and interesting collection than would a traditional list of 10. I'll admit, I haven't seen every comic book movie released, but I have seen every one that's been released that I plan on seeing (meaning that if I haven't seen a movie by now, I probably never will, because I've heard it sucks).
But first, I'll clarify what I mean by "comic book movies". For the purpose of this list, a comic book movie is any feature length film whose story and/or characters originally appeared in a comic book (and a comic book includes comics, comic strips, graphic novels, or manga). So films with comic book themes that didn't originate in the world of comics, such as The Incredibles, Unbreakable, or Hancock, don't qualify. Nor do sci-fi-ish properties that originated elsewhere but have since become comic books, such as Transformers.
The other thing I should clarify is what I mean by "top". In this, I'm mostly judging the films by the quality of the films themselves, and less so by how strong they are as adaptations, although that will obviously come into play. The reason this isn't simply a list on the best adaptations is twofold: one, I haven't read all the source material for every comic book movie, and two, some movies don't necessarily adapt one source as much as they borrow from several (that said, if I have read the source material, it would obviously affect my opinion of the film). Other than that, "top" is an amalgamation between "best" and "favourite". And now, on to the list...