Red Dead Redemption's sound effects and soundtrack are both top-notch. The music has the appropriate "old west" theme, and the sound effects are so subtle and appropriate that they make you feel as if you're actually there.
For more information on the winner, read our review of Red Dead Redemption.
Mass Effect 2
Mass Effect 2 has plenty going for it in the gameplay department, but its sound is certainly one of the most memorable aspects. There was plenty of drama in the game, and with a score that bordered on absolutely epic, players felt emotionally connected from start to finish through the tale of Commander Sheppard and the crew of the Normandy.