Most of my favorites have already been mentioned already. Wolf 3D, Doom, Tie Fighter. Daggerfall, too. I didn't play that one nearly as much as Morrowind or Oblivion, though. I loved the two Terminator games of theirs that I played back then. Future Shock and Skynet. Both were made using the same engine that was used for Daggerfall. They were buggy, like most Bethesda games, but a lot of fun.