The below post is a response from Nicolas Dorier to post #7! As it keeps being updated.

Keep in mind Nicolas has developed a near complete rewrite of Bitcoin core, authored a book on Bitcoin development and also made minor contributions to very important Bitcoin improvement proposals, such as segwit.

Nicolas Dorier:

I think that people bashing C# does not know what they are talking about.
Java is very much retarded language, with lots of over engineered libraries and not as portable as C#.

Also, the user base of C# is comparable to Java. (http://stackoverflow.com/tags)
No even mentioning Unity which is the most popular gaming dev plateform.

Take a look at my book about NBitcoin on http://n.bitcoin.ninja/ and enjoy cross plateform bitcoin development without headache