I'm an Emacs fanboy, personally, but Emacs is just a tool. It won't make you a better programmer any more than a super-fancy pen will make you a better writer.
The clarification that "great programmers" adapt their environment to themselves may have some merit, but lots of tools can do that (e.g. vim and SlickEdit), so there's nothing particular about Emacs in that regard.
I think what's most likely true is that "great programmers" are passionate about programming and people who are passionate about it tend to find tools that help drive that passion. Emacs (and vim and SlickEdit, et al) is such a tool.
