Good:
F.E.A.R. Online (free for just multiplayer, the single player campaign you have to pay for, but it's worth it if you like suspense, and gore, and flipping your chair over backwards at least twice from something jumping out at you.)
TrackMania Nations Forever (if you've never heard of this, look it up)
America's Army (yeah, don't hate)
SPORE (it's single player mostly, but you still share everything you create in that game with all the other players in the world)
Bad:
idk, i'm not picky like most.
h3r3 c0m3 t3h fl4m3xz0rz?!??