As some of you may have noticed, today marked the 76th anniversary of Howard Phillips Lovecraft's death in 1937. H.P. Lovecraft's work has had a huge impact not only on the horror genre, but has also inspired a large number of popular video and tabletop games. The Call of Cthulhu roleplaying game, first published in 1981, was the first commercial game to adapt the work of H.P. Lovecraft*. There is little doubt that this game influenced all Lovecraftian games that came after it, and that it contributed greatly to Lovecraft's influence on popular culture. Looking around the web, I found a great post on RPG Geek by Sandy Peterson, the author of the Call of Cthulhuroleplaying game. In it he discusses the process of adapting Lovecraft's stories into an roleplaying game, and how the Call of Cthulhu roleplaying game into being.
Read Sandy's post here.
*Note: While I recognize that one Dungeons and Dragons supplement did Lovecraftian dieties in 1980, this was not the focus of the game, and it didn't adapt the tone of Lovecraft's work.