My wife and I played Halo 3 for the first time in almost 280 days last week (its the only game we use match making on, and our last suggested friends were that long ago). We weren't too bad, but its no fun if you're not playing with friends. We used to be able to get a whole Big Team together and even if we got destroyed, it was like old times in the dorm.
We might be willing to play some H3 with you guys, but we prefer L4D2 ourselves, as we love cooperatively beating down the computer.