It's hard to think of what the worlds of Gaming and Fantasy would be like if it wasn't for this man. Regardless of if you like his actual work (ie, first edition AD&D) you've been touched by something that resulted from it. Essentially all roleplaying games, and RPG style computer games. For good or ill, there would be no World of Warcraft without Gygax. But more than that, the very longevity of the fantasy genre and it's persistent tropes - they have been propped up and kept alive by fantasy gaming. Sure, he stole from Tolkien, Leiber, Howard, Vance, and many other authors, but D&D turned Wizards, Dragons, and Elves from something featured in a few books and into a world you could explore and be a part of. In the process inspiring thousands more books...
PodCastle would never exist were it not for Gygax. Here's to his legacy!