Superheroes

I'm watching my new DVD of Superman Returns, and it prompted the question: are the superhero movies, book adaptations? The movies aren't based on storylines from the comic books, but they include characters we all got to know in the comics. I'm leaning toward no. Not because I don't consider the comics "real books." But for the same reason I would not consider the travesty of the made-for-tv-movie, Anne of Green Gables: the Continuing Story, an adaptation of the Anne books (unlike the wonderful first movie in the series). The only things that movie had in common with the books were the character names, just like the superhero movies. So the Superman, Batman, X-Men, Spider Man movies are not adaptations in my opinion.