I was going to suggest Neal Adams as another possibility. I'm not the biggest fan of his work, but I do acknowledge that he is one of the industry greats that influenced others.
I just Googled for lists of top writers, and this site I regularly go to (Mania) gave these top 20:
20. (tie) Mark Millar and Jim Starlin
19. Steve Engleheart
18. Warren Ellis
17. Mark Waid
16. Marv Wolfman
15. Peter David
14. Kurt Busiek
13. John Byrne
12. Gardner Fox
11. Garth Ennis
10. Geoff Johns
9. Chris Claremont
8. Len Wein
7. Neil Gaiman
6. Denny O'Neill
5. Grant Morrison
4. Roy Thomas
3. Frank Miller
2. Stan Lee
1. Alan Moore
Honorable Mentions went to the following:
Dave Sim – Creator of Cerebus the Aardvark
Carl Barks – longtime writer of writer of Donald Duck stories for Disney
Gilbert Hernandez – creator of acclaimed independent series Love & Rockets
Will Eisner – creator of the Spirit
Bill Finger – early writer of the Golden Age Batman and Green Lantern stories
J.M. DeMatteis – one of comics more underrated writers. Wrote “Kraven’s Last Hunt”
James Robinson – One of today’s best comic writers and a guy I can see making the list one day
Steve Gerber – One of Marvels best of the 70s and creator of Howard the Duck
Jim Shooter – The former controversial Marvel Editor-in-Chief was also a very accomplished writer.
Chuck Dixon – Long time writer of the Punisher and Detective Comics among others. One of the better writers when it comes to gritty crime tales
Keith Giffen – writer of the post-crisis more humorous Justice Leage, Legion of Super Heroes and many others.
Mike Mignola – Creator of Hellboy
Jack Kirby – Co-creator with Stan Lee on many of Marvels greatest characters. Created Kamandi, OMAC, and the New Gods titles at DC.
Roger Stern – Longtime writer on the Avengers, Spider-Man, Dr. Strange, Action Comics, etc…
You can read the list (and the comments by fans) here:
http://www.mania.com/top-20-comic-writers-all-time_article_115430.htmlFor artists, Atlas Comics made the following list (for American Comic Books):
10. Lou Fine
9. Bernard Krigstein
8. Steve Ditko
7. Frank Frazetta
6. Wally Wood
5. Harvey Kurtzman
4. Carl Barks
3. Neal Adams
2. Will Eisner
1. Jack Kirby
That list can be found here:
http://www.acomics.com/best10.htmI post these not to start arguments (I by no means agree with everything on these lists; shoot - I didn't even
KNOW some of these people), but to throw a bunch of other names out for the discussion.