It doesn't really matter what games you started out playing- the people who designed them were making homages to Gygax's work, interpreting it in their own way.
Some are more angst-heavy (Vampire), some are more kill-heavy (Warhammer 40K), but they all stem from the basic wargames turned roleplaying that Gygax started in his basement.
Every gaming, roleplaying, and video convention stems from his Convention 0- before him, nerds didn't get together in big groups like that, unless it was for some appliance convention.
Gygax wasn't a huge fan of later versions of D&D, though. He always felt (and argued constantly) that having to know six sourcebooks of information to play a game was just too many rules- it was exclusionary, and did more damage than it did help the cause of gaming. That's one thing that I've found to be true- every time I'm teaching a new person to play a game, I can look at my D&D books, and describe to them in one or two sentences each of the different player classes and races. In order to teach someone to play Shadowrun, they have to sit down and read the entire SR3 (or SR4) sourcebook, or they're a worthless player who runs around with Ruger Superwarhawk in their hand and an assault rifle on their back.
As a result, you see a lot more people who pick up D&D "to try something fun and new" than you do Shadowrun. Which I think is sad, because I love the dirty smelly dystopian future of Shadowrun, and the reflections of the real world in it.
-kv
