Microsoft sees a different role for themselves in games than the other two. Nintendo relies solely on game revenues to survive so they dominate their platform. Sony also relies heavily on game revenue to show profit in the space so they tend to dominate.
Microsoft sees their role as a platform provider and a game profiter second. So, they focus on providing the platform more then pumping out IPs. If you look closely at their new releases it is clear that Microsoft is relying heavily on 3rd parties to develop software and they see their role in building games as one that puts features in games to sell the platform.
As for IPs you mentioned... The former FASA IPs are licensed by the former founder of FASA and MechWarrior has a new game on the way. It was announced last summer.