Prints were made on an Epson 7880 using PS3 and later 6.
Different subjects, different lighting, but same lens (Hass. V 150 CF). Lighting was strobe, hard key. Both cropped to 20x30. Say F11, maybe 8.
This was not a test, just an observation. I couldn't remember which camera was used on each print until I went to the file. Subject matter was portraits, which is of course less demanding on fine detail than say landscapes. Lots of flat areas that are essentially volume.
Another observation: Leica M8 files hold up well to enlargement, say to 16x24. Mostly. That sensor could have some rough aliasing artifacts that look like detail until you try to uprez, which can result in odd shapes in grass and other fine detail.
The D800e can go larger, of course, and I'm not making prints for sale.
At print sizes up to 20x30" I see no significant difference between a D800e and 5D2. In a print.
That would depends a great deal on how the prints were made - processing and print technology, how the interpolation was done and on what surface the photos were printed on.
Were the exposures made of the identical subjects in identical lighting with (as near as possible identical lenses and camera settings? were they processed the same way? Clearly the 36mp images will not have to interpolated as much as the ones from the 5D Mark II to print at 20 x 30 inches.