System Shock 2 has made IGN's Top 100 Games of All Time (Cross Platform). It's ranked #041.
For those of you who missed out, System Shock 2 was released in Aug. '99, and it was an FPS/RPG hybrid. The games graphics were overall a little dated for its time, however one thing it had in spades was atmosphere. It made excellent use of lighting to provide a creepy feel, and it had one of the best sound mixes in its day, as well as making excellent use of EAX, Creative Labs Environmental Audio Extensions, for very realistic sound.
Playing this baby at 2:00 am with all the lights out and the sounds up, it was freakier than Doom 3 is today. Amazing, amazing title.