In February, Microsoft is holding the Xbox Live Arcade House Party to continue its tradition of quality downloadable releases. Started February 16th with Konami's Hard Corpse: Uprising, a Contra game btw, they will then weekly release one of five games. the biggest of which is the 2003 critical darling Beyond Good and Evil now in glorious HD and much easier to find than on the used market. The other hit coming to the XBLA is the 2009 Diablo-like click fest of Torchlight. Also rocking out at the party is PopCap's Bejewled Blitz Live and Microsoft's Full House Poker.
This isn't to say all of these, other than Microsoft's Full House Poker, are Microsoft exclusive. Beyond Good and Evil HD will also be released on the PS3, so it is foreseeable that some of the other 3rd party games will be multiplatform releases. Whether they will be simultaneous like Costume Quest or temporary exclusives like Castle Crashers is yet to be known.