Without D&D there would BE no other RPGs. It was the first of its kind
White Wolf's Vampire RPG owes more to Call Of Cthulhu in terms of system, but ultimately...
After D&D set the ball rolling, those that followed first and fast were (IIRC) Traveller (The prototype space age RPG), Call Of Cthulhu (The prototype horror RPG), Runequest (Like D&D but with a % system), Tunnels & Trolls (Fighting Fantasy probably owes everything to the T&T single player game books). I just wish I could remember the first post-apocalyptic one... Annoying to me that I cannot, though I didn't play it very much. Top Secret/SI was the prototype spy game, for lovers of Alpha Protocol, BTW
However - D&D invented the RPG. That's why they all ultimately derive from it. No genre, no games
