In the late 80's I played a game called The Colony. Long before Wolfenstein 3D or Doom a lone developer named David Alan Smith created a game in which you help the survivors of a remote space colony.
For a look at what one of the first 3d action games looked like just watch David A. Smith demo the game on youtube (part 1) (part 2). I have many memories of moving slowly down hallways and wondering where the next alien might be. There were many immersive worlds and environments to come but The Colony was my first taste of what games would be like.
If you're interested in the story behind The Colony, and some of the technical details that made it very advanced for its time, David A Smith has written My Colony Memoir. It's hard to imagine a single person working on a computer that didn't even have complete development tools building a complete game from scratch. Especially since we live in the era of huge budget games created by huge teams of specialists. Sometimes it's good to remember what can be done on a small machine by one person.