I regularly visit DxOMark for statistical data before seeking my next lens or considering a new body. (No - the equipment does not make or break your images, but while you can technically cut a steak with spoon it is much easier, faster, and precise with a sharp finely honed blade..)
What I am unfortunately seeing in some of your verbal assessments of late is the comparisons seem 'fanboyish'. When the 'older equipment' information is presented like an obituary and the newer equipment reads like the front page of a tabloid you could hardly consider that an unbiased 3rd party perspective. Specifically the comparison of the 5DmkII.
Before anyone starts thinking 'Canon fanboy rant!' I own both Canon and Nikon equipment. Through inheritance, adoption, or simply hooking up with a spouse that prefers another brand I have ended up with two Canon bodies (60D/5DmkII) and two Nikon bodies (D300s/D700) not to mention a healthy amount of glass for each. My gripe is simply when I see comments and comparisons made with verbiage designed to imply superiority over another even when the differences are slight or nonexistent.
In this comparison it is obvious that someone at DxO prefers Nikon in this context, and even the simple listing of data shows it. O.o
In this 'paper' comparison it would have been nice to have relevant information added and/or embellished:
The images produced by the 5DmkII and its 'lowly' 21mp are superb, there is no sharpness lacking that cannot be achieved with better glass (certainly something that will be a major factor with the 36mp sensor of the D800). So to automatically hypothesize that the D800 sensor will meet expectations or be superior because it has more pixels is absurd, especially as you have not even tested the D800 yet.
You at least described the ISO range evenly without adding or leaving out relevant data to favor one or the other.
AF - Lets be honest, you do not need any more than one AF point and place it over the subject you want to be in focus. Quality images rely more on composition than focus. While the 5DmkII appears to be lacking in number you do not include the same description of its components. Artificially emphasizing some inferiority of the 5DmkII by stating no more than the number of its points even though there is relevant data for its AF mechanism and that all points are cross type - and that there are additional 'hidden' points that assist in the evaluative focus and tracking. I will certainly give kudos to Nikon though for their servo tracking mode, it is indeed superior to Canon across all models. I enjoy it a great deal on my D300s and D700 when shooting wildlife, especially birds. Though to be fair in handing out praise I have to say that my two Canon bodies, and all the way down the Rebel line I have used, all appear to focus faster on average. So even though they may have less focus points in each tier something is working more effectively.
Metering? Nothing more than two different ways to get to the same point. I have never encountered a metering issue that could not be adjusted where it needs to be, and have had to make adjustments for both brands. Not sure about the scene recognition and its role in face detection AF, played with it on a lower Nikon model without any lasting impression.
If you wish to make any comparisons for video capabilities please at least mention where they differ! Both bodies do full HD video, have the same frame rates at 1080p, and with the same input/output options sans the raw HDMI output (though available on the 5DmkII with Magic Lantern.) The main differences are the cropped modes (magnification) offered by the D800, and 60fps at 720p - versus the full manual exposure control provided by canon. Whether trading either of these features for the other will make you go with one over the other can only be determined by the user.
Yes the viewfinder is larger on the D800 (100% vs 98%), but does it really make any difference to the image that one has a tiny bit smaller view? No it does not. Now if one were larger than the actual capture area, and you ended up cropping off parts of the scene you thought you were getting, that would be an issue! At this level you are doing post processing 95% of the time anyway, if you got something in the shot around the border on the 5DmkII you did not want just clip it off... Both are big and bright and display relevant shooting data. The 5DmkII allows you to change out the focus screens for specialized needs. -moot
They both have the same display, why you felt the need to add viewing angle for one and not the other just reads like one is inferior. Not only are they the same, but Canon has been offering that lcd for longer and across more models than Nikon. Not to mention that Canon's display does not pixelate when zooming into the last two or three magnifications like Nikon. (hopefully they have changed that in the D800)
The frame rate is identical for any practical measurement for the exception that the frame rate does not increase on the D800 with the addition of any other accessories, it increases when shooting in DX cropped mode.
I will give the point to Nikon for the flash. I know many people who say a pop up flash does not belong on a pro body. All I can tell you is that I use it often on my D700 for a little fill in the field and wish my 5DmkII had one.
Both have external flash sync. Not sure what you are describing as if it were any different. (wireless commander mode maybe?)
Weight - Canon is lighter, both have magnesium bodies.
Battery life - About the same at this level from any manufacturer. (Though Sony would be the only other manufacturer of a 'compact' body FF, and no longer considered in this tier as it does not offer video.)
If you are going to even mention price, Canon is the winner. Outstanding image quality and broadcast video for ~$800 less currently. If more mp, more post processing, pop up flash, and digital video zoom are worth ~$800 then by all means get the Nikon.
Weather sealing - You do not mention anything about the 5DmkII as if it does not have any environmental sealing, which it certainly does. Can we please let this issue go already..? The number of equipment review sites that incorrectly imply there was no additional sealing or body improvements from the original 5D is staggering, and just emphasizes the lack of experience and knowledge the reviewer has with the product being reviewed. I have had all four of my cameras out in the rain, crawling through dew soaked grass, spilled drinks on/around them, been splashed around the pool, lake, beach, etc and never had an issue with any of the higher end bodies from Nikon or Canon. None of them are waterproof, they all have some level of sealing, all things being considered the only thing you need to be overly concerned with is your lenses.