Easily Halo 2 - it launched at the perfect time and had a vastly superior skill system to Halo 3. In Halo 3 you were able to get stuck at a certain level if you won too much - because the system wasnt able to calculate just wins. We had 130 straight wins at one point and were forced to get on new GT's and throw a couple of matches to get somewhere. Also, you didnt have the party chat option on the original xbox - meaning that basically everyone was in match chat. Party chat really ruined multiplayer on consoles.