OLD D40x , D60 and D90's have the best results compared to newer generation DSLR's
That is due to lesser density Sensors.. but people are people who believe in numbers.
10 mp D80 deliver much better "sharper" image than D90 with 12.9mp.
any good camera having above 2 mp sensor is just more than enough for Incredible images .
With higher density sensors there are lot of artifacts like smudging ,colour fringes,etc etc
but kind of allurement which a modern camera offer cannot be overlooked,like stop photography ,interface,compatibility ,ease of use,ruggedness which may not be as much in older cameras.
If I need Tack sharp pictures I would go for D80 , I want incredible colur renderings I would choose D90 or D300.
one can go for d7000 for its additional video capabilities and resolutions means bigger picture and more room for cropping..
Pro camera:- D700 with 12.1 mp is the best camera i ever found in market.
when it comes to canon they are good in Ps cameras. they are exceptionally good for sports and journalism use for thier fast cameras.. but Nikon have an upper edge in it when it comes to dslr .