I had the two : the 20 D was much better, not just because 2 more Mp , but because the 10D was a slow camera. The 20D was snappier. After that I skip the 30 D and 40 D and went to the 50 D (not the best one of the XX family)
Yep. The 50D was a bit lack-lustre. An OK camera, not one of the greats.
Just for fun, I'll list all the Canon cameras I have owned from best to worst (trying to make allowances for the year of manufacture)
* 5D IV - The best DSLR ever made
* 20D - wonderful cameras, I had two and wore them both out
* 1D IV - still going strong and still takes a great picture
* 7D - a tour de force when released and still a worthy camera to this day
* 7D II - a fitting successor to the excellent 7D Mark 1
* 5DS R - slow and a bit clunky, but awesome image quality
* G9X II A great little pocket camera
* 1D III - a better camera than history says, the AF issues were quite uncommon
* 5D II - fantastic sensor, would be close to top-of-list but stone-age AF system
* Powershot A95 - very small, very practical. Good camera.
* 40D - just a 20D with a extra pixels but a decent workhorse
* 50D - just a 40D with a extra pixels and worse high ISO
*450D - too many compromises made this unpleasant to use. Good for the price.
* EOS R - Let down by awful ergonomics, bad viewfinder, and unreliable AF