Compared to...

Studio scene comparison (JPEG)

This is our standard studio scene comparison shot taken from exactly the same tripod position. Lighting: daylight simulation, >98% CRI. Crops are 100%. Ambient temperature was approximately 22°C (~72°F).

Nikon D200 vs. Canon EOS 5D

Camera settings:

• Nikon D200: Nikkor 50 mm F1.8 lens, Aperture Priority, ISO 100
  JPEG Large/Fine, Manual WB, Default Parameters (Normal), Self-Timer
   
• Canon EOS 5D: Canon EF 85 mm F1.8 lens, Aperture Priority,
  ISO 100, JPEG Large/Fine, Manual WB, Default Parameters (Standard PS), Self-Timer

Nikon D200	Canon EOS 5D
4,236 KB JPEG (3872 x 2592)	4,969 KB JPEG (4992 x 3328)

Here the resolution advantage is reversed, the EOS 5D carrying a 25% megapixel advantage. This combined with the D200's default conservative sharpening mean that the EOS 5D's image looks much more detailed and crisper.

Nikon D200 (High sharpening) vs. Canon EOS 5D

Camera settings:

• Nikon D200: Nikkor 50 mm F1.8 lens, Aperture Priority, ISO 100
  JPEG Large/Fine, Manual WB, Custom Parameters (High sharpening), Self-Timer
   
• Canon EOS 5D: Canon EF 85 mm F1.8 lens, Aperture Priority,
  ISO 100, JPEG Large/Fine, Manual WB, Default Parameters (Standard PS), Self-Timer

Nikon D200 (High sharpening)	Canon EOS 5D
4,586 KB JPEG (3872 x 2592)	4,969 KB JPEG (4992 x 3328)

Equalizing the sharpening a little things are closer, but the EOS 5D still exhibits an advantage in resolving fine detail (see the tree on the Bailey's label). That said you have to ask yourself is this a 'double the price' advantage, to me at least it is not.