When I first found out about the topic, I immediately went in two separate directions (which is not unusual for me…).
The first was to go with characters: Superman, Spiderman, Batman, and Savage Dragon. They are each Iconic, and each defines their era in comic book history. Superman heralds the Golden Age, while I feel Spider-man represents the changes happening in comics during the 60’s and 70’s. Batman is the foundation of the Dark and Gritty trends of the 80’s and early 90’s, even though he had his origin alongside Supes.
Rounding out this foursome, I think Savage Dragon represents everything that Image Comics’ founders wanted to do, and so few actually have managed. Spawn, Walking Dead and Invincible may have higher sales numbers than Savage Dragon, but the audience for the book is loyal, and the quality has mostly remained consistent from the beginning. I would happily replace this character with Cerberus, Bone, or possibly even Spawn, to be honest, but I think Eric Larson deserves the nod. Also - Head fin!
The other direction I took involved the actual men and women who created these characters. Will Eisner, Jack Kirby, Stan Lee and either Alan Moore or Julius ‘Julie’ Schwartz each have contributed hugely to the medium of comics and the way that illustrated storytelling has evolved, though I would probably choose Moore over Schwartz for purely beardy reasons.