System Shock 2 takes place 40 years after the events on Citadel Station, aboard the first human starship, the Von Braun, shortly after it's arrival at Tau Ceti. Shodan makes Tycho and Durandal seem about as crazy and scary as Bob Newhart. The emphasis is on hacking and stealth, but there is a healthy dose of combat as well. You play a hacker aboard Citadel station who must defeat Shodan's plans and eventually destroy her.
Shodan has created an army of biologically-engineered and cybernetic creatures (including mutated and augmented members of the Citadel crew) and is planning to wipe out all human life on Earth. System Shock takes place on an orbital habitat called Citadel Station which has been taken over by an insane AI called Shodan.
The System Shock series was made by basically the same team that brought us Thief:The Dark project and Warren Spector, who of course created Deus Ex. Think Deus Ex crossed with Marathon and you have a general idea of the atmosphere and game mechanics. Both feature deep and intelligent storylines, rampant/insane AIs, and a very tense, dark, scary atmosphere. There are numerous similarities between the System Shock and Marathon series. : noticed the similarities between the 2 system shocks and marathon games? : games before, but I don't remember what was said.
: I think I remember hearing the marathon community discuss the PC system shock In Response To: Are the System Shock games.