Sid Meier is one of the best and certainly one of my most favourite game designers, and the work he and Bruce Shelley put into Civilization blew my freaking mind back in the day.
I was obsessed with this damn game. You know how some people would see falling Tetris blocks while looking at buildings after they first get bitten by the Tetris bug? I was like that with Civ. Everything I saw was somehow related to Civ. Bus to school? Civ. Packet of chips? Civ. Playing any other game? CIV.