.Hack or SAO...Yuki Kajiura will be there to provide the epic world music.
SAO is on everyone's recent memory in the anime community, even to such a point you seldom see any reviewers even mentioning their similarities. we may not see big name support immediately, but let's hope for some basic support for something like GuildWars2, ElderScrolls, and maybe even something like a NeedForSpeed or Gran Turismo. MS could knock one out of the park by buying like a hundred of these things, adapting them to the Xbox ONE + Kinect; and maybe do a cursory plug-in to something like Fable.