As far as 360 multiplayer goes, I have Halo 3, and Halo Reach, but I play both with the skill of a mentally deficient kindergartner who's missing two fingers, so I'd hesitate to play either online. XD
I also have Tekken 6, Super Street Fighter 4, and Soul Calibur 4. the first two I own for both 360 and PS3, the last only for the PS3, but I don't think this is a fighting game crowd. ^^