If you didn't strip the binaries there is some hope as IDA Pro can produce C-alike code for you to work with. Usually it is very rough though, at least when I used it a couple of years ago.
information is discarded in the compiling process. Even if a decompiler could produce the logical equivalent code with classes and everything (it probably can't), the self-documenting part is gone in optimized release code. No variable names, no routine names, no class names - just addresses.