I don't think comics that aren't about superheroes are something that cant be done or are rare. I mean, the sunday comics aren't always about superheroes. Most of them aren't. Y the last Man isn't about some superpowered alien who fights criminals, but it is one of the best comics I've ever read. The Walking Dead too, if you could count that. It does involve zombies, but thats about as close as it gets to being like a superhero comic.