*sigh*

1. They mean superhero movies
2. Superhero isn't a genre, it's a style. You can do superhero horror movies, superhero spy thrillers, superhero romance. Most of superhero movies are action/adventure, but that's the genre right there.
3. People have no clue how many movies are comic book movies. Juno, From Hell, 300, The Crow, Extraction, Ghost World, A History of Violence, Edge of Tomorrow....