Your result seems fair considering that the 20D is two thirds the price of the D200.
Apples and oranges. You get what you pay for.
5D = $4700 / 12Mp
D200 = $2700 / 10Mp
20D = $1900 / 8.2Mp
350D = $1400 / 8Mp
What is interesting is your finding on the sharpness, what did you have it set to? DP review had this to say:
Nikon D200 in-camera sharpness
As we've already commented the D200's default in-camera sharpness (Auto or Normal) is too mild to deliver the detail actually captured. Hence in these comparisons we have provided comparisons to a D200 shot taken using the 'Normal' parameters preset and also one with sharpness set to 'High' (+2) which helps to equalize the difference in sharpening between it and other cameras.
EDIT: Things look worse for the D200 in the luminance noise but better in the chroma noise according to this review:
http://www.dpreview.com/reviews/canoneos30d/page20.asp