System Shock 2 was one of those games no one really liked until everyone decided they did. Upon its original release, it received rave reviews, then promptly sunk without a trace. Then Bioshock came out, was a big hit and everyone decided to see what they'd been missing in the meanwhile (and promptly questioned why Bioshock wasn't as detailed or in-depth as its ancestor). Still, better late than never, unless you're a former member of developers Looking Glass Studios who, sadly, folded soon after.
Despite being, essentially, a survival horror game, albeit one played from a first-person perspective, Looking Glass decided not to go for the standard 'soundtrack made of creepy noises' approach, and instead went with something a little different. The OST consists primarily of a mix of dance, drum and bass and electronica, and this difference makes it stand out in a field of me-toos in the wake of Silent Hill, a game that showed everyone how grinding metal and chugging noises should be done - lessons that pretty much everyone ignored or didn't quite get thereafter. Ops 2 is a great example of this approach - in game it accentuates the feelings of loneliness and isolation you'll experience. Out of the game, it becomes a stand-out track from a stand-out OST.