Can I compile mpich 3 with gcc 4.9 on Mavericks?
Yes, luck was had!

Why not install homebrew and let that handle the compiling for you?

That would be the easiest way to install mpich.

If you insist on compiling manually, you would have to provide information on where the configure programs hangs. I.e. what is the output of the program (take a look in the configure log).