I'm not sure why, since I never even played the game that much when it came out, but the soundtrack to Diablo II takes me way back anytime I hear it. It is single-handedly enough to make me [want to] download and play the game again, and I can listen to the standalone album without being bored by a single track. It's one of the few older video game soundtracks I've never found cheesy or stale, no matter how many listens I give it.
What piece of music or soundtrack from a game has this effect on you?