Ruby seems like a bad basis of comparison, as it appears to be designed without concern for runtime speed at all and the main implementation uses a slow, simple

Ruby seems like a bad basis of comparison, as it appears to be designed without concern for runtime speed at all and the main implementation uses a slow, simple design. High-level languages in general can be very fast, but it doesn't mean any particular one is. C# and Java can produce very efficient programs, and for a lot of CPU-bound problems the obvious solution in either of those will be faster, particularly stuff that needs to perform lots of little allocations or where the obvious C++ program does too much accidental copying.