It seems like this thread suffers from lots of people using various different definitions for “fantasy.”
Fantasy: Do comic book movies resemble what the average non-fan on the street would recognize as fantasy? Is it “high fantasy” with magic and knights and badly written pseudo-medieval accents? Some of them, but only some. Even Thor is “an alien” in more modern stories. There’s crossover with these typical “fantastical” elements, including Thor’s “Thee art mine enemy now-eth!” talk, but this is more the exception. It seems to me that for every “My power is magic!” character, there are five “Impossible super chemicals/radiation/technology gave me this ability!” Modern-set fantasy novels again seem to focus on calling on attributes from these stories with modern twists, but the protagonist is a ‘witch’ or ‘wizard’ calling on ancient powers and not a ‘scientist.’
Fantasy: Are comic books about made up things? Other than autobiographies and the like, yes. Superhero stories? I certainly hope so! If we’re using this definition, describing things that didn’t happen, all fiction is fantasy. If we’re just using “things happen that are impossible or couldn’t happen in ‘our’ world,” again, this is still a huge portion of fiction including the majority of what’s considered science fiction. This definition is only useful if you want to use a different, more colorful word to mean “pretend.”
Fantasy: Do comic books offer themes of escapism through fantastical elements? Sometimes, although people seem to take it for granted, given how many comic book characters have sad sack lives, and how many comic books are focused on being “edgy” by showing horrible things happening to people. I wouldn’t step into these comic book worlds, myself, even if I were promised a superpower.
Fantasy: Are super-hero comic books stupid smelly things for stupid babies and now that we’re all 14 we can totes tell the babies how stupid their baby likes are so we feel more grown up? Yeah, okay, most of us age out of that, but why not.
Speculative Fiction: I just saw Sunny Daze mention this term while editing, and it seems an excellent compromise to me. A lot of “light” science fiction is referred to with this term now, along with some alt-history, some fantasy… It seems that it would really cover most of the superhero genre, without the potential confusion of meaning a variety of definitions for “fantasy story.” If the story starts as space adventure, then lands on Sorceror’s World, it’s still the same genre, speculative!