In my opinion, Peter Davidson never suited the role, but Colin Baker's era was so badly botched that his was the worst as far as broadcast goes. If every Doctor had the same high level of production, I would probably say Peter Davidson. He was a bit too... well, just normal to be "The Doctor".

I would order The Doctors as so...

12. Peter Davidson.
11. Colin Baker.
10. William Hartnell.
9. John Hurt.
8. Paul McGann.
7. Patrick Troughton.
6. Chris Eccleston.
5. David Tennant.
4. Sylvester McCoy.
3. Jon Pertwee.
2. Tom Baker.
1. Matt Smith.

And really the top nine are all great and Hartnell could be magical too.