In terms of influence, draftsmanship, inventiveness. You could also list more.

Trying to be objective:

1. Will Eisner
2. Jack Kirby
3. Osamu Tezuka
4. R Crumb
5. Harvey Kurtzman
6. Dave Sim
7. Moebius
8. Frank Miller
9. Jim Steranko
10. Neal Adams

My personal taste:

1. Kyle Baker
2. Kim Deitch
3. John Hicklenton
4. Kevin O'Neill
5. JH Williams
6. Marc Hempel
7. Kentaro Miura
8. David Chelsea
9. Dave McKean
10. Michael Zulli