5DII vs 5DIII vs D800 (side-by-side)

You could say EF mount is better by addition of the adapter . But if you are comparing like this then NEX mount, m4/3 and even nikon 1 CX mount will beat EF mount because they can mount more lenses then EF mount with adapter.

See? Can I say m4/3 is better than EF mount?

Perhaps you should specify clearly "EF mount + adapter" is better than "F mount + adapter". It would be more fair.

If you just consider the mount alone (WithOUT adapter), EF mount is a loser. EF mount can just mount EF lens, not EF-S lens, not FD lens. However, F mount can mount FX lens, DX lens and also old AI lens directly. That's why Nikon boys love F mount and you should respect it.