C++ is still alive and kicking. Even good old C still is used in the industry for a reason. However C# developer demand is rising and far outnumbers C and C++. Chances are you have less problems getting a job if you know C#.
If I were you I'd ask myself what I want to later, because the fields in informatics to some extent dictate the language. Here is a *rough* breakdown..
C#: Mostly windows applications. Some XBox and PC game-dev as well.
C++. Jack of all trades language. You'll find applications, system and embedded programming, scientific stuff. De-facto standard for game-dev.
C: Language of choice for embedded and DSP stuff. If you want to go into automotive, avionic or medical world this is the language of choice.
But keep in mind, that the language you use is just a language to express your software-designs. It's much more important to learn and train your problem solving skills. These btw are language-agnostic. Knowing how to approach a problem is what makes up a good prgrammer, not knowing your language of choice inside out.
This skill can't be tought. You need years of practice to develop it.
Btw - The industry expects that you're able to pick up a new language fast.
If a project needs for example C and Java skills, and you're familiar with C only you get a month at most to get into Java well enough to be productive. (this does of course not include in-depth knowledge of the libraries, but in practice you need only a small part per project anyway).