I've tried to argue this point time and time again. The 5D2 isn't as good as anything regarding the 5D3. The 5D2 isn't a bad camera. The 5D3 just happens to be better, at everything.
Landscape shot, tripod mounted, manually focused, ISO 100. How is the 5DIII better?
(If you say 'becuase it has one more MP', I'll scream... )
Reduced shadow noise. You can push the files a lot more.
And one more MP.