Compare the popularity of C# + VB.net to other languages to see .NET has less than 1/20th of the market. And that for a company that not so long ago dominated the software market.
.NET is useless for
* desktop applications, since the forward and backward compatibility is not guaranteed.
* Downloadable applications, because a 250mb library pack download is just too much.
* Web Startups and/or social applications, because of the (sql) server costs.
So the only use .NET has is for small corporate applications.
The only thing Silverlight is good for is playing DRM protected media.