They promise 15, that much I remember in first year
Yup 15 MS Studios games. Curious if they'll hit it. So far we have:
Forza 5
Dead Rising 3
Ryse
Kinect Sports Rivals
Crimson Dragon
Killer Instinct
Max: Curse of the Brotherhood
Zoo Tycoon
Powerstar Golf
Super Time Force (was MS Studios but moved to ID@Xbox program)
Project Spark
Xbox Fitness
Still to come in 2014:
Sunset Overdrive
Forza Horizon 2 (maybe?)
Halo Master Chief Collection
Quantum Break (probably not)
Fable Legends (maybe in beta before end of the year)
Looks like they might get to the 15 game promise depending on how you look at things. You can maybe knock off Max and Zoo Tycoon, but I think both came to XB1 before 360. Also, Xbox Fitness isn't really a game and Super Time Force was moved to ID@Xbox so it's not an MS Studios game for the XB1 version.
EDIT: How could I forget LocoCycle?