I actually think both franchises tend to lack in the music department. The original had a pretty competant score (and Halo 2 had some moments of brilliance as well) but overall I'd say the music in Halo is unimpressive. I think Marin O Donnell creates really generic and uninspired music. The score for Mass Effect is in the same situation. I think it's lifeless, the music only works to "tug at your heartstrings" rather than express any true emotion. I would say games like Castlevania, Metal Gear (excluding MGS2 and MGS4), and the Streets of Rage series have much more interesting music that not only works to assist the mood of the game but is listenable on its own.