Rapture is not so much an abandoned underwater city, the inhabitants just went a bit crazy, to say the least. I just think the team like and are good at making games that are isolated, claustrophobic, tense and dripping with atmosphere. I dunno if I'll ever get around to checking out System Shock 2 (too many other games coming out and limited time) but if I do and I get stuck installing, I'll let you know thanks
Isn't there a popular mod for it which vastly upgrades the models and textures?