Superheroes have been, mostly, historically loners, singular individuals with powers that inevitably make people view them as saviors and even messiahs--the comics spend a lot of time navel-gazing over the "superhero trap". Peoples' need for help is infinite, while even a superhero is a finite resource. I think that comic book superheros fulfill a quasi-religious role in today's society.

That's buttressed by your observation of the simultaneous rise of the zombies. How Manichean! The shambling dark horde opposed by an army of superheros, banded into The Avengers and Justice League and League of Tomorrow (or whatever, they blend together after a while).

I'd also have to note that comic superheroes are usually vigilantes who scorn democratic institutions. Even when they band together, their secret organizations usually work against established governments; or they suborn institutions, like Batman's relationship with Commissioner Gordon. They're authoritarians that way, and in a time when authoritarianism is looking increasingly attractive to some, superheroes are attractive embodiments of the will to power and impulse to unfettered action.

Is there some deep, psychosocial phenomenon manifesting itself here? A group psychosis propagating via pop culture?Are we, as a culture, expressing some need to confront the world with some godlike power because we feel it has become increasingly impossible to deal with its madness in any other way?

Most of the paragraph is about modern existential terror, but right there in the middle you hit upon the timeless allure of the comic super hero "to confront the world with some godlike power". The comics make the first-person point of view of someone who possesses god-like powers accessible to the pimply-faced nerd bullied at school. He's empowered in his imagination to shoot lasers from his eyes and to smite his enemies but good!

And how blasphemous would it be to imagine yourself as Jesus doing exactly the same? Religions vigorously discourage that kind of thinking, so comics have a distinct marketing edge in their willingness to deliver the forbidden drug of deity-envy.

It occurs to me that I'm using the term "comic" to describe two increasingly divergent art forms. The movies and videos use CGI to imbue their stories with the same gaudy fluorescence of the traditional printed genre, and you'd think they'd be replacing comic books by simply beating them at their own game. But the book form hasn't gone away, and it's made the transition to ebooks seamlessly. In fact, to my eye, a comic on a screen is even more vivid than they could ever be on cheap pulp. It doesn't matter that the images don't move, they seem to have retained their magical appeal in the digital age. So far.