I like the soundtrack of Freelancer, Amnesia, Half-Life. Star Wars games I guess they use the movie's orchestral scores. Warcraft 3 and Starcraft's soundtracks were great, in their context. Deus ex is indeed cool, i've been missing out all this time.
It would also help to know what kind of music you and your friends are interested in, some tracks may be hits and some may not be. I have a plethora of music, mostly video game music, and while helpful in making suggestions it is also a hinderance since it's just such a vast ammount of varying styles and quality.