I dont think canon need to answer anything. 90% of reviews top it out as the best dslr ever. There are a percentage of shooters here who complain about it's dynamic range etc and while this may be a valid point it seems it is only an issue for a very small percentage of actual users. Its a small percentage on potn and I am sure that potn is probably only 1% of canon users.
I think for the majority of users noise and speed and focus are some of the major points. The 5d is great here, but the d800 is also, and from trying it would say its only letdown is the 4fps, if that concerns you. Sure it doesn't have a focus system as hyped or configurable as the 5d, but it is still great. I also think that the big files is not as big a deal for some as others, or indeed it is becoming less of an issue as storage gets cheaper and processors get better.
Indeed i would say the iso gap between the two models isn't as wide as often said. yes, the 5d is cleaner, but if you process a raw file and save both at required print size at say 3600 pixels by 2400 pixels for a 12 x 8, it be hard to tell which camera took which at iso 6400.
Both have strengths, bith have weaknesses, but to be fair both are great