I vote David Tennessee by a mile. He was great, and actually made me a huge Dr. Who fan for the period he was on. Chistoper Eccleston was terrible, and Matt Smith is just a little bit better than Eccleston. I haven't seen any of the Dr's prior to these 3.
My prediction threads:
Wii U will sell under 40m units (made on 14th September 2012)
PS Vita will sell under 20m units (made on 30th September 2012)
Wii U will sell under 7m in 2013 - I was right