To be fair, I've probably only beaten ME3 7 times.

(edit: but I did get 400+ hours in multiplayer, which was fantastic)
ME1 I probably played 6 or 7 times before 2 even came out. I did my first run, then a renegade run, then a pure paragon run, then a straight evil renegade run… that kind of thing. Try all the classes, get all the achievements. You can beat ME1 in like 15 hours if you're speed reading and skipping side quests.
ME2 is my favorite game of all time, so same kind of thing. All classes, keeping a squad mate along on every mission to get all their dialogue, etc. DLC would come out and it'd give me an excuse to play again. I probably beat it 3 times in a row when it first came out.
Also, being a poor college student, it's not like I had unlimited options!