Usually i am happy with the games own soundtrack, the Original music of a game is part of the package of experience the developers want to give us, so i try not to alter it.
( if you dont agree with me , start up a survival horror game, favourable one without or with only few weapons,like Amnesia, now flee from the monsters while listening to the benny hill theme http://www.youtube.com/watch?v=MK6TXMsvgQg )
I only mute it and listen to my own if i dont care about immersive athmosphere and story. For example in dull hackn slay games (I cant imagine playing Diablo without Blind Guardian) or if it is a game i can enjoy but it has a horrible horrible soundtrack ( i got a nice library of fantasy athmo- and soundtrack music).
But @ Vault101 your Fallout as well as Far Cry choices are definatly great
