C# has yet to drive meaningful business value for Microsoft. It certainly didn't topple Java the way they hoped it would, and it didn't even manage to gain internal mindshare for Windows Vista and Windows 7 apps. There's XNA, but that's not for the big triple-A titles. Despite the best efforts of the Developer Division, Microsoft's cash cows are still powered by C++, C++, C++.
You have absolutely no idea just how many internal enterprise applications are developed in C#. You don't see them, being that they are internal enterprise applications, but they do exist. And it's a huge market.
