Which does not fit into a genre neatly any more than most of them do, because of the world-building issues.
SF attempts to suspend disbelief by appeal to the authority of science. Fantasy, by internal consistency. Superhero stories tend to run on the established tropes of the field. Nice and circular.
Like the origin stories, which are kinda random. An alien sent by his parents from their exploding planet. An Amazon sent by Greek gods to help the modern world. A man fanatic enough to acquire crime-fighting skills by training and rich enough to buy the best gadgets to help. A man who had a lab accident involving chemicals and lightning. A man given a super-powerful ring by a dying alien. . .
Meta-origins were a late afterthought.
But part of that is that if a writer starts to get all organized, it starts to shift toward another genre. Endow your characters with technological powers, and it shifts toward science fiction, or steampunk. The genetic origin also, if less so. Draw on common folklore themes like werewolvery and vampirism, and it shifts toward urban fantasy. Consistent high fantasy magic makes it halfway high fantasy and halfway urban. The cheerful chaos is what keeps it in the superhero genre.