I want to start a debate. Who are the four greatest superhero characters? Not who is, at the moment, most popular. Really think about it. For example, my four favorite characters are Batman, Daredevil, Green Lantern (Hal Jordan), and Captain America. But I would only classify one of them as being one of the four on Mount Rushmore. To me, there are three characters who should not be debated, but feel free to convince me I'm wrong.
Superman is the Godfather of the comic book industry. Without him, we wouldn't be where we are today. Take a moment to thank Kal for all that us geeks have. Created by Jerry Siegel and Joe Shuster, Superman has been whooping baddies and saving kittens since 1938. If anyone deserves to be on this, it is him. One of, if not the biggest events in comic book history is "The Death of Superman." It is one of the highest selling books in the history of the industry.
I will start this off by telling you that I am a Batman fanatic. He is the GODDAMN Batman! Superman may have started the industry, but this guy has sustained it. No other character has been developed as much as Batman. "The Dark Knight Returns" is one of the most important and influential books introduced to the medium back in the 80's. Like the Joker said in "The Dark Knight," Batman "changed things." The medium would not be what it is today without that book, so thank Frank Miller. Thank him for Year One too. I just want to give a shout out to Bob Kane and Bill Finger for creating the best, most badass, crusading, sometimes campy, and all around awesome SUPERhero we have today. Becasue of Batman, we have characters like the Joker, who very well could be on this mountain of mine if he wasn't psychotic. Batman, by himself, could sustain a comic book company. Gotham City is the greatest city within any comic book universe. The city is a character in its own right. Nightwing, Robin, Batgirl, Red Robin, Red Hood, Batwoman, Birds of Prey, Batwing, etc. exist because of Batman. Superman and the rest of the DC Universe exists because Batman allows it.
Spiderman first swung on to the scene in 1962. Thank you Stan Lee and Steve Ditko. He is one of the first teenagers to be considered a superhero. Spiderman is important, because he was probably the first superhero created that a lot of young people could relate to. He is to Marvel what Superman and Batman are to DC. In my opinion, Spiderman has one of the best villain bases as well, coming second to only Batman.
Those are the three where I don't think a reasonable debate can be made to kick them off. The fourth spot is up for grabs as far as I'm concerned. If I had to pick it would either be Wonder Woman or Hulk.