I wouldn't buy a D800 because of the 4fps - that is to slow for what I need. My friend and I go shooting together and we have totally different styles - he has a 5DIII and thinks it is the dog's b's - over the weekend he wasnt trying to get the moment when a glider was just lifting off when being towed - which was when the full 10fps was needed. Horses for courses.
Why not consider D800 a 5fps camera? Yes, with a grip and DX crop but that's still cheaper than the 5D3 with more pixels!
What's really amazing is that somehow some people rate 1fps difference more precious than 36MP and 14.5 stops of dynamic range... Wow...
Well then again you get the extra FPS but at a cost. Sometimes it's more important to others, sometimes not. Sometimes color rendition is more important, which canon is generally better from most testers, sometimes the AF, which canon takes the slight edge assuming you don't need the F8 shooting with certain lens combos. Sometimes the processing, video, and ergonomics are more important. Sometimes it's the service that matters or the other lens options. No one is equal and others will prefer the nikons latitude and extra workflow needed to handle 36mp files are more important. It is what it is.
There are probably 3 different camps of photographers who actually are able to afford these cameras. 15-20% there the canon is best for what they shoot, how they shoot and needs and expectations. 15-20% whom the Nikon rules. And 60-70% whom either camera would suffice and go over and beyond their own personal experience level. No one camp is more correct than the other and it doesn't make one better than others, it just is the way it is.