Interesting question.
Thing is, Superheroes, as a genre, have a lot going for them. They can be made to appeal to a more socially aware audience quite easily - we're seeing it now with gender or culture swapping characters. It's something that is more problematic in other genres - especially historically based ones like Westerns.
And, frankly, Westerns just have zero appeal outside of the American market which makes them a dead end going forward.
Science Fiction is problematic because the Chinese market is rife with minefields - no time travel stories for example.
Video game crossovers? Sure, it's a genre that has generally failed in the past with some spectacularly bad movies, but, then again, the same could be said for superhero movies. Because video games are so ubiquitous across so many different cultures, you'd think if they could finally hit on a right video game movie, they'd manage to open up the genre.