Mass Effect 1 was poorly ported to PC, the lighting in particular looks completely different than the X360 version for no apparent reason. The 360 version is bright and colorful while the PC port has muted and muddied colors. And then there's the incessent audio issues plaguing the PC version. I'm not sure if it was my old Audigy 2ZS or not but audio was buggered to all hell - Shepard's gun was waaay louder than everything else, and the cutscenes would occsaionally be silent or near-silent with only "footsteps" being audible...etc. Very annoying, although that was somewhat minor (it didn't detract too much from an otherwise awesome game).
Anyway, love ME1 and it is definitely great on the PC. It just could have been that much better had the porting issues been worked out. I should try it on my Realtek onbard audio sometime, I haven't fired it up since I ditched the old Audigy 2ZS...