For very simple games (e.g. character input/output), any language would do.
For indie games, look for game developer kits, and those languages (C/C++, C#, Python)
For working on a big game project at a big game company, you'll probably need C/C++ or maybe C#.
If you'd want to do video card programming, you'd need to learn HLSL, CG or similar.
And there are other languages used for scripting, such as Lua, Python, shell scripts, bash, etc.
You might need to create extensions for your pipeline, such as Visual Studio, Maya, ZBursh, etc (C# is needed for Visual Studio extensions).
So there's no single answer. You'd probably need many languages to learn.
Start with C# and Unity for indie games. Check this out.