My friend bought me the Mass Effect trilogy this past Christmas for the PC. Until then, I knew nothing about Mass Effect.
Now... I'm just purely addicted. I've done 2 playthrough's already of the trilogy and starting the third one whenever I have free time from school
The storyline is so immersive and the fact that you can alter Shepard to be who YOU want to be. Haven't played a game with this awesome of a campaign ever. I haven't even touched multiplayer on ME3 yet.