The other side of the whole "questioning the superheroic world" coin is what if you DO have amazing powers, but the world pretty much stays the same? What if you're not in a major metropolitan area? I mean, Durham, NC has a downtown, but I think the most terrible thing that happens there is the local popsicle place failed to open up for summer. (Seriously, it was a big deal. There was almost a riot of one.)
Sure, there's petty theft and drugs, like any city, but we have no Lex Luthor that I'm aware of. We don't really need a superhero. Obviously, for there to be a superhero, there has to be a supervillain. Either someone cursed with weird powers or disfigured or so smart he or she goes mad. If there's one without the other, the world will be largely lopsided.
If there's a hero without a villain, then a lot of kittens get down from trees and gang violence goes away. (Actually, that gang violence elimination thing would be pretty cool.) We'd have some protection from natural disasters, I guess, if the hero can change the weather or earthquakes, and we'd clear out petty crime, and then what? There's not a lot of other vigilante work to do. Superheroes almost always steer clear of international conflicts (except for a few who specifically are soldiers) so helping the army is likely out. Unless they get a job as security detail, they would get fat and bored. They'd become one of those old people in nursing homes talking about the glory days, only they'd be doing it at age 35.
"Dammit, I JUST filled in for that broken trellis bridge! Is the city going to fix it? What are my tax dollars for, anyway?"
The city, too, could get complacent, sure that the hero would save the day. I believe the Powerpuff Girls covered this plotline.
On the other hand, if there's a villain without a hero, then society devolves into a world best suited to the villain's demeanor. If it were the Joker, we'd all die in chaotic violence. If it were Lex Luthor, I assume we'd have an ambitious society that encouraged competition, with a totalitarian dictator who never leaves office and who constantly looks for someone to have a pissing contest with. Very likely to end in intergalactic war.
Of course, we've seen parodies of total villain domination, where the bad guy wins, gets masses of wealth and power, and feels unfulfilled because the true fun was in the battle, not the winning. (See Megamind for an amusing take on this thread.) I think that kind of plot does more to justify the need for villains for the audience, saying that too much power on one side is either dangerous or boring. (Also this is why you should never kill the Joker. Or Darth Maul.)
These days we must have more suspension of disbelief than ever to fully enjoy superhero stories. Perhaps we're done with our current suspension of disbelief and we need something new. We're in the post-grit world, where we've already read about heroes who aren't squeaky clean and may even have drugs, alcohol, or other personal issues. Including Batman, who wasn't always OCD and batshit (Hah. Batshit. Ahem.) crazy, is now considered dangerous to both enemies and allies.
I'm wondering what we should add to this hero bag of tricks. Powers, alter egos, need for balance, those are all necessary, but now I think we need more in order to keep the genre alive. DC has rebooted everything. Webcomics are raising thousands (or even over a million) dollars to fund their own storytelling. Parodies are now considered legitimate tropes for storytelling. My favorite comics aren't even the superhero books (I'll talk Locke and Key, Chew, and Unwritten some other time.) Not putting superheroes to bed entirely, but a different take on heroes. I think Knight and Squire was onto something, and wish Astro City would return.
Till then, I will re-read my comics, go back to dreaming of my town having its own superhero, choose flight over invisibility again, and keep my eyes peeled for any emerging super villain.