I think the absolute worst thing that could happen to superhero movies is if too FEW of them start getting released. On it's head that statement might sound insane, but hear me out.
I think almost everyone is in agreement that the current trend of zombie themed movies (horror and otherwise) has run its course, saturated the market and holds very little current value to potential fans. Most people think of zombies as played out, and that everything that can be done with them has. But if you are one of the people that is sick of this current trend (and for the sake of this argument I'm counting on the fact that you are) what are you really sick of?
Are you sick of movies like Warm Bodies, that bring a young adult romantic comedy sensibility to the genre, with a retelling of Romeo and Juliet? Are you sick of dark coming of age stories like "Dead Girl" which features a single zombie that serves as the starting point of an exploration of who people really are when no one's looking? Is it shows like "The Walking Dead" that explore long term implications of living in a zombie apocalypse, and how people would deal with it once they got over the shock of it all?
Or is it the vast and increasing number of lazy retreads of George Romero's "of the Dead" series, especially "Night of the Living Dead?"
I think that right there demonstrates the principle I'm getting at. For decades there were never more than a few small active adaptations of superheroes going at any given time. Granted at this time the genre had substantially less depth in the source material, with stories never having much more depth than "hero fights villain," "hero fights natural disaster," or "hero takes part in love triangle."
For decades that's all you saw in adaptations, well that and endless origin stories. Don't get me wrong, origin stories can serve a purpose. They define the underlying motivation of a hero/heroine/group of heroes and serve as an entry point for an audience to imagine a world close to their own offering a jumping off point after which the leaps the story expects them to take are more acceptable.
But at the end of the day, there's a reason that one of the defining characteristics of the villain in the film that allowed superheroes to turn a corner as a genre had the defining characteristic of mocking origin stories as a concept. All of them wind up being very similar. Stan Lee basically admits to writing the same origin over a dozen times for many of the key Marvel characters.
Creators often treat the origin as a simple means to have a character that can do the things they want them to do. They're not written with the intent of being the best story the character ever takes part in. seeing as successful characters often last for decades and hundreds of stories, it would be very sad if it were.
Back when the genre wasn't well represented in film, often there were stretches of several years without an entry from the genre and usually any year where one was released there were never more than five in a single year. In these cases they were almost always origin stories, and if watched back to back they were all essentially the same movie. For a long time this was all Hollywood knew how to do, which is why every franchise floundered when it went past four installments.
Honestly what allowed this to turn the corner was Christopher Nolan's expanded world building of "The Dark Knight trilogy" and Marvel's expanded universe films. Films where good, if safe, versions of all the major character's origins were released to give everyone context, and then once that was done, the gloves came off and they could start doing real stories that actually took chances.
Things like this are the difference between seeing dozens of different versions of the same movie, and films of varying quality within a genre. When there's a good foundation a genre becomes a structure by which people can use a set of trappings to tell whatever kind of story they'd like. It's at this point that you start to see the really great stories/works emerge and the formulaic ones simply become intolerable.
When I hear people complain that there are too many superhero movies, I can just see the genre getting its wings clipped right as it truly gets ready to soar. But it's at this point that I can only hope that someday the phrase "there are just too many superhero movies out" sounds just as strange as "there are too many comedies out."