Java being more widely deployed has to worry about source and binary compatibilities between all the supported versions and thus for them, changing the bytecode would have been a painful decision.

As opposed to that C# did not have to worry about these things due to their limited deploy base and could freely change the language and/or the VM without worrying about backward compatibility.

That does not mean java is a better language than C# - its just that when Sun woke up and started adding features to the language, it was not easy.