C# requires very heavy weight dependencies, .NET on Windows, and Mono on everything else. You are looking at increasing your install process upwards of a gigabyte or more. Although it is possible to use C# on non windows systems I wouldn't really call it a practical solution. There is always Java but my personal opinion is that this can cause some slight lag in the loading process (traditionally Java performs a bit slower than C++ due to the interpreter that must intercept and parse the byte code). If you are using lightweight graphics and don't mind adding a few extra seconds to your loading screens I would recommend java. If performance is critical your a little stuck with C++.
I'm curious under what circumstances you would ever need even close to 1GB or more space using C# under any OS? The Client Profile for 4.0 which is all you need to do most projects (unless you need some really obscure .NET features--unlikely), is a 30MB download in its entirety, and mono can be even smaller.
C# won't require a bigger set of dependencies than Java would. It's more than a practical solution these days.