Ever since I played Quake for the first time, I realized what sound can do for a video-game. That was the first (and pretty much only) time I almost forgot there was music playing, for it all fit so well. I was visibly shaking when I first played Quake, mouse and keyboard abolutely soaked with cold sweat.
However, the audio-experience that came with Quake was largely unique in that they put a LOT of care into it. Sound for me is vitally important, but nothing is more annoying than crap-soundtracks that get into the 'annoying' spectrum. A great example of this is in (almost) every RPG. One minute you're enjoying the atmosphere, both visually and audibly, then suddenly you enter combat and some 15s ditty starts repeating until you feel like exploring how far you can push a Q-Tip into your ears. It's at that point sound tends to get muted while my mp3 player (wmp, WinAmp, etc.) gets employed to give me my own soundtrack to the game, a sure sign of failure in the audio-department.
At that, I would say in MOST cases, more effort should be put into games atmosphere and environmental ambience over music in exception to those rare titles that realize this fault and change their audio-scheme to something more appropriate.
As an after-thought, to this day I still enjoy the Quake-soundtrack. That Game-disc has had more plays than any other album in my collection. But then again, TReznor is a genius imho.