Jeffrey's comment is spot on.
Languages is just a means to express your ideas. The more languages you learn (within reasonable limit) the better your understanding of what matters when you translate your idea in a program. Each languages has strength and weaknesses and each in their own way tried to tackle a particular set of difficulties inherent into translating creative thought in structured formal implementation. But while focusing on these specific aspects they often left out other aspects.
Each language you learn will bring you a better understanding of what programming is all about.
That said it is also good to be proficient in a language but I would rather employ someone that is good in 5 languages rather than an expert in one that have never experienced at least one more.
Also, though now C# seems to clearly have the upper hand and is favoured amongst employers it will eventually peak and fade away in favour of a newer better language. Multiple cores are evolving fast now, I can see in less than 10 years appearing processors with 100+ cores, yet still now it is very difficult to program multi threaded application. I would not be surprised that a new programming paradigm would emerge and a new language written for it that would make it natural to use massive parallelism.
So, your first instinct was good, that is to get into C++ and C#. If you have the chance to see Java then you would know probably the three most used (or sought after) languages in the industry today, this can only be good for you. I suggest you continue this trend but try languages that support a different paradigm. Now that you know C# you can go for functional programming and try F#, I guarantee it will change the way you see programming. If you know Java try out aspect oriented and AspectJ. Duck-Typing with Python... the list goes on. Each time you will have learned something you could not had you stick with just one language.
I started with just one (C++) and when I switched to Java I thought it was for good. Serendipity had me exposed to many other languages and I have never learned as much and as fast as in these times. Now I always keep an opportunistic eye and ear to jump at the occasion to add another under my belt, not so much for employability (I would NOT want a job in Delphi) but just for personal enlightenment because every times it makes me better at the languages I work in every day.