In American Comics, there were few with the stature and body of work he had. Bob Andelman wrote upon his death that, "Will Eisner didn't create Superman, Batman, Spider-Man or even Archie and Jughead. Some comic book fans may scratch their heads when asked to describe his work. But every artist and writer in comic books, as well as graphic artists across the entire spectrum of modern illustration, television and film, owes a debt to him."
Read the rest here.
If you've near seen his work, you can check it out here. Not everything he did was to my taste, but that isn't a bad thing.