HL original. Was simply a brilliant expereince, got it on early release - typical shop posting out early, and as a result had a 4 digit WON ID which was always kool. No game has ever just been so amazing for it's time, it really did set the standard for the future - HL2 is great too but nowhere near as ground breaking!
Stalker 1 and 2, Crysis 1 and 2, Far cry 1 and 2, both Dooms and all 4 Fear games. But none of them top Half -Life 2 imo. Your right about Deus Ex tho'. Old but Epic.
