it shows that the Canon lens is better, nothing else
put a sigma 35/1,4 or a nikon 85/1,4 etc on a d800
Yeah, but that's a pretty significant something. A 24-70/2.8 is a very popular lens for a lot of good reasons, and a prime just doesn't cut it in a lot of situations. The fact that the D800 + Nikon 24-70/2.8 doesn't offer a whole lot more real
resolution than a 5DIII + Canon 24-70 II is just one example of diminishing returns with increasing resolution. Plus, of course, there's more to taking a picture than system resolution.
It will be interesting to see if Nikon comes out with a new 24-70, and how the Canon 24-70 II will perform on a future (hypothetical) high MP body from Canon.