Mine would be the eleventh (matt Smith) as he played an eccentric timelord who looked young but acted old very well, and he had a tough act to follow but succeeded and i would also pick the third doctor (Jon Pertwee) as he played a good action hero. David Tennant was pretty cool aswell.
Would be much easier to tell you I detested Sylvester McCoy and not keen on Matt Smith.
The rest, from Willaim Hartnell to David Tennant brought something new to each re-incarnation.
Patrick Troughton - he was just the right level of eccentric and humourous, and also William Hartnell, I was nine when DH started, and it made a big impact one me.
William H. looked really old, but I have found out since he was a year younger than I am now!!!
and also, just because i am interested, how do you think Peter Capaldi will do? I for one think that he will be pretty good. He may take a while to get used too but i think he will be good.
Andy...same for me. Hartnell was the best, although Tom Baker was funnier.
Its the same with James Bond...Connery was easily the best although, controversially, I quite George Lazenby. I know, he probably only has one fan and thats me !