One of the problems is that Canon have released a specialist camera (1Dx, action) and a general-purpose camera (5D3), whereas Nikon have released two specialist cameras (D4 for action, D800 for high-resolution), but the Nikon high-resolution specialist camera has the Canon general-purpose camera beaten on spec in most areas. That is, the specialist body beats the general-purpose camera for most applications, as well as being unmatched in its own specialty.
The 5D3 would be much better, and well worth its $3500USD asking price, if Canon made three minor changes, which would have made for a much more capable camera while reducing R&D and manufacturing costs:
1) Full weather sealing, equal to the 1D line. Rubber gaskets cost a few cents. They'd need to test the weather sealing equally whether it was fully sealed or only partly sealed, so no savings to be made in R&D either.
2) Implemented the same AF system as in the 1Dx (including f/8 focusing), not a cut-down version. Saves cost on R&D (only one system to develop and test) and manufacturing (only one line of AF to produce, not two) and gives better performance. Then it would have been Canon's top-of-the-line AF versus Nikon's top-of-the-line AF, and history tells us they'll be very close. I can't see Canon's second-tier AF beating Nikon's top-of-the-line AF, even if it has ten more AF points.
3) Optimised the sharpness/NR/AA filter purely for stills. Release a second video version if they wish, but optimise the main line for stills.
These three, easy changes would have made it the best general-purpose camera on the market, ceding no ground to Nikon except for high-megapixel applications (and there's a 40MP sensor floating around in prototypes - one marked '5D Mark II' and with a 45-point AF system seemingly from the 1D4 - for that) and making it well worth the $3500. Sure, it may have stolen a few sales from the 1Dx (unlikely, as the 1Dx appears to be a high-frame-rate action specialist) but would have made it the best general-purpose still camera on the market, no contest, and guaranteed a lot of lens sales which would otherwise go to Nikon.
As it is, though, the Nikon high-resolution specialist camera has the Canon general-purpose camera beaten for most general-purpose applications.