Dark Forces isn't just a great FPS, but a great Star Wars game too. The aesthetic, story, and missions all capture the feeling of the original trilogy perfectly, while still finding plenty of room to chart it's own path through a galaxy far, far away.

Edit: forgot to mention I played this with the new source port, The Force Engine. Had a few visual glitches but overall it's incredible and long overdue for this game. Highly recommend using it if the DOS era clunkiness turned you off from the game.