As Jay said, Maya is increasing in use in the Games Industry. The only Game I know of that used XSI fully, was Half Life 2. Otherwise its just used here and there, as Maya is currently. Also Maya is mostly used for its animations tools and dynamics. Most Models/Assets are still generally created in Max. But as I said earlier, choice of applications are made by Art Directors and "Heads of Sheds" at the birth of a project.

There were a lot of rumours about what would happen to Maya when Autodesk bought Alias, but as most rumours are, it was all bull. Would you want to be the head of a company to be blaimed for the demise of the King of 3D Apps? Not Me...