Is Half-Life (the original), System Shock 1/2 or Deus Ex the most revolutionary within their genres?
I think Half-Life and System Shock were more a triumph of atmosphere and production values, whereas Deus Ex was a revolutionary change to game architecture. The degree of freedom Deus Ex gave you to approach problems was incredible, and it also made the game more immersive (I remember searching for Illuminati on the internet while playing it, scribbling clues down on bits of paper). Best game ever.
