If you're talking comic books, Neal Adams is first and I guess Bill Finger would be second. Which is a shame as he was always second fiddle to so many in the Golden Age. He was a major influence in the creation of several major DC heroes and villains and never got the credit for it.

If you're talking comic strips obviously Schulz tops the list but second is a toughy. George Herriman was a huge influence when I was very young. Berk Breathed and Bloom County taught me politics could be funny. Watterson made me feel good while it lasted. But all time second place? I'm going to go with Herriman just because I've been reading his stuff the longest and it seems to always be my fall back when I look for inspiration. Plus, I can only dream of people still reading and discussing my work 66 years after I'm gone.