"it ended as one where nobody had to die"

I think the conclusion here is a bit over-determined, but there's still something to it -- the current success of superhero flicks has a lot to do with Americans wanting to "re-write" 9/11:

"Superhero films are the dominant cinematic force right now. They make money hand over fist, and their releases turn into genuine pop culture events. But we miss their point — we miss the why of them. These films are pop culture's most sustained response to tragedy. In the wake of the 9/11 terrorist attacks, America turned to superpowered heroes to rewrite that day so that it ended as one where nobody had to die.

Superhero movies, in some ways, aim to turn that day into something out of myth, like the ancients might have recast a real tragedy as an epic tale of heroism. This is one of the ways we process grief — in our tales.

And the further we get into the cinematic superhero era — now almost 15 years long — the more explicit these films get about both their real-world impetus and about the way America responded to that tragedy."

I agree with a lot of this, but the argument works best with the New York-centric Avengers and Avengers-affiliated films.  The writer does admit that our current superhero boom actually began before 9/11 with Blade in 1998 and the first X-Men in 2000.

There's a more simple explanation as well -- first, CGI got good enough in the 90's for people flying around in ridiculous costumes to be a little more palatable and, second, the divide between "children's" and "adult" entertainment pretty much disappeared as Gen X and Y came of age with a healthy hunger for the stuff they grew up on.

(And this is part of the reason we're doomed to endless sequels and re-boots for the next 30 years at least.)