The people you talked to don't know what they are talking about. C# is a very similar language to Java, all told; it has most of the same benefits and drawbacks. The way it all works is pretty similar (Java/C# is compiled into an intermediate language/bytecode that is interpreted or JIT compiled to native code, with various similar optimizations that you don't need to worry about as a programmer). It's used in a lot of the same situations as Java, and is really aimed for the same market. It's moving a lot faster and bringing in a lot of innovation as a language, but it's (in practice) pretty much Windows-only, if that's a concern of yours. The job market is similar. Both are very popular languages.
As for a language to learn, I would suggest something DIFFERENT. You say you know C++ and Java; C# shouldn't be hard to pick up. Potential employers will know this. Try Scala or Python. Both will give you some new perspectives on things (C# not so much), and make you a better programmer by teaching you new ways to think, rather than just adding another tool to your box.
