Burnout 3's soundtrack, though filled with crap suited the game quite well i thoguht. Right pace, sound etc. The game is great though i should add. You don't have to like the music for it to suit the scenario after all.
For UT any song with lyrics wouldn't work well for a start because all the players and anouncers in UT speak and it's at random times, thus the music can't match up to it. Mid chorus you'd have a "Double Kill" etc. As Arsenalvendetta has already said.
The music needs to be music, not a song, there's a difference, also it should be ambient and add to the fighting and the pace not be an advert for a band. ANYWAY and most important of all UT2004 has an in built mp3 player and there's no reason to assume Envy wouldn't so... It'd be your choice what you listen too.
Bunging a soundtrack filled with bands and.. all that gump would only alienate all the players who don't like any one or two of the list of bands and it'd be a waste of cash getting the licenses for that i believe.