Hands down, Metal Gear Solid 2: Sons of Liberty. Those who disagree will be shot on sight. Get on Kazaa and download the theme song, you will agree. Get over to your nearest Blockbuster and rent the game. Chop, chop.
Heh. I never got around to playing that, however I think I might soon be changing my decision, because right now on my playlist Aeris' Theme from Final Fantasy VII just started playing... bringing back memories. Harrison Gregson-Williams and Nobuo Uematsu are both geniouses. If they worked on a piece together, my head would explode from the greatness and from sticking it in microwaves so many times.