Both Java and C# tried to break the web (silverlight and Java FX) and both ended up being considerable failures.

We still don't have a reasonably easy way to write cross-platform applications (Mac/Win/Lin/Phone) in a native-first language. The reason JS has taken off is because it filled a rather HUGE hole.

If there is a chance that is changing, let us know, but right now, the hole isn't being filled with anything else.