Realistically, what is the biggest franchise that Microsoft can buy out that would give them first place in console sales?

[sweetoothj]

Microsoft already has three big blockbuster franchises. Halo, Gears of War and now Minecraft. However, I don't think this will be enough for Microsoft to be first place. What franchise could achieve this? I think overall, only COD will be able to do this. Maybe GTA, but that isn't a yearly title.