Play it coop, there's little original MP games out there
I'm gonna be brief on this one, as there are a lot of reviews for this game. As you may have read this game is superb in a lot of ways. It's a very proud role game: in contrast to the average, there is more than just kill or stealth, there is at least hacking and "psyching" too. The role factor is enough important that can make you play the game twice or even three times. There is also a very good story driven by a very well voice-acted journals; you even have two villains for the price of one and each of the levels will be different and full of surprises. Wow!, this is a hell of a game, and if you like complex games with good stories (with poor graphics though), this one is at the top, just read the titles of the reviews, there is no negative one, and "best", "great" and "ever" (and "scary") are usual words.
I'm going to talk about some concrete aspect of the game: I'm going to propose you to play it with friends. Think for a moment about multiplayer games, think on games that you have play MP or know how are their MP modes. I can count no more than two or three different type of multiplayer games, you have games like Unreal Tournament, some like Rainbow Six or Hidden & Dangerous 2 (very enjoyable game), that are based on killing the enemy or defeating him in some way, sometimes in very sophisticated ways. And there is too the games based on role playing (90% of them in some tolkien-esque world), with the MMORPG as the most usual type. But there is always something I have miss when playing some good game with a good story and it is that I can't play it with friends. Normally you play it at the same time as some friend and then you talk about it with him/her later, but it's not the same. Well, as far as I know, System Shock 2 is the only game you can play the SP levels in MP, I mean, you can follow the story playing with your friends. plus, it's a role-playing game, which means that every one of the player can play different and complement the others.
How many times have you play Thief, for example, and thought "it would be awesome if I could play this level with a friend as another thief"? or with Hitman, or with Deus Ex or with any other story-driven game or something-more-than-just-killing game? SS2 has it and it was one of my best gaming experiences. You know, every time you play some role-playing game, most of the time you wander what would happen if your character were different, imagine now that you have them all. In SS2 you can play the game in 3-4 different ways (not only kill and stealth), but you can also play it with 3-4 friends (no more than 4 possible) and make different kind of characters. When I played it, we were three, one "psi", one mechanic/hacker and one bad-ass marine. We played it with a voice software, so we could talk while playing. The experience was really fun, I remember once, when we entered some cutscene, when one of the villains (the biological one) tries to play with your mind I started screaming and the others started asking what was happening until they entered too. You can't have this kind of fun when your only tasks are killing and defending and little more.
Well..., graphics and movements are very low in quality specially if you play it now. The rest is more than average.
The Bottom Line
This is, finally, a game that makes something as easy as letting the players play the main story both in SP and in MP. Of course, there should be more, like Quake II, for example, but, as a role playing game with a complex story, a frightening ambiance, different ways of solving problems and labyrinthic levels, this is an MP experience you can't miss.