Doom 2 is the sequel to arguably the first real FPS, DOOM. 'Nuff said.
You can find a good version of the OST here.
This soundtrack hardly needs any introduction, it's probably one of the most well-known games and music out there. There's an endless list of covers to be found only, and with good reason: the compositions by Robert Prince contain an awesome mix of hard-hitting, screaming rock and creepy, atmospheric music.
The song of the first level (Running From Evil) contains some great guitar soloing and drum work..usually the first level is finished before the solo, but the song returns in level 15 =)
While just giving the game a spin or putting on the mp3s is good fun, it's also nice to see what others have done with it, like: