Braid and Castle Crashers are both great choices. You really can't go wrong with either, or both. The patch is up so that means online should be functional. I'll also jump in a game with you if you like. I'll be trying out the co-op for the first time myself online.
Instead of just giving you good multiplayer games, I'll give you the multiplayer games I have and play, so you know if you get the same ones, we can be multiplayer buddies. 
Gears of War 2
Call of Duty: World at War(my favorite online)
Burnout Paradise(My second favorite online)
Fable II
Virtua Fighter 5 Online
Forza 2(I don't actually play this, so don't bother asking me.)
All Pro Football 2K8
Marvel Ultimate Alliance
Grand Theft Auto IV
How is the wheel by the way? I've been thinking of getting one to play Burnout with but it's an expensive thing and I want to make sure it's worth it.
Tag: Became a freaking mod and a complete douche, coincidentally, at the same time.
