I'm just going to focus on Xbox.
1) A disastrous launch with all that DRM nonsense
2) Not following through on Kinect
3) Mismanaging Halo after Bungie left
4) Mismanaging Rare/Rare's IPs
5) Closing Lionhead and robbing the world of Fable
6) Lackluster first-party software in general
7) Buying timed exclusives