Though most are unaware of it, the backlog of great IP that MS owns or has access too is enormous, not to mention the opportunity for exciting new IP.
At the end of the day it will come down to resourcing. How badly does Microsoft want to make the X1 a huge success from a gaming perspective? If they resource games properly, each individual one could be excellent enough to be profitable. If they resources ENOUGH games properly, they could also lead the X1 to victory.
starcraft - Playing Games = FUN, Talking about Games = SERIOUS