For me, a game without music is a game without a soul. Mass Effect 2 has probably some of the best music I've ever heard. Try playing the suicide mission with no sound; it's just not right.
So. Would anyone like to vote on what they believe were the best music pieces from Mass Effect 2? Bearing in mind the official soundtrack misses off some really good ones.
If I were to pick my favourites, I would say the spaceport battle music from Horizon, the "Long Walk" music, Garrus' track, Samara's track, Tali's track (surprise) and of course, the ending theme.