Day 4 of the non-D&D Blog Challenge
Gygax never impressed me with his writing...it just never clicked. So I guess my answer is, "Quite a few".
Since I'm not really part of the OSR community, nor do I play OSR games, I don't know how much of a pedestal Gygax is put up on. I acknowledge that he is, for all practical intent and purpose, the father of the roleplaying hobby. I was starstruck in the way that only a teenage nerd can be when I met him at a convention in the late '80s. But my experience sitting down with Mike Pondsmith for something like 45 minutes at a convention was a much greater influence on me. The authors who have impressed me is a long list and growing, and include - in no particular order - Kenneth Hite, Robin D. Laws, Fred Hicks, Josh Mosqueira, Marc Vezina, Greg Stafford, Steve Perrin, Sandy Petersen, Cam Banks, David Pulver, S. John Ross, and many, many more.