Ground-breaking games Atari Adventure (actually 1979), Rogue, and Mystery House
Cody and Jeremy have both mentioned these games as blueprints for what would follow later. I wonder also if we can discuss the games themselves. In 1980, people weren't thinking, "Gee, I can't wait until someone invents Mario Kart." These games were as innovative, in their own way, as the titles we looked at from 1993.