Tom Baker: Number one!! Jon Pertwee would be my second.
Peter Davidson was the worst (the yuppie Doctor). Colin (sorry, TE) was the second most boring to me. All he had right was the brillo pad hair!
The last Doctor (in the last millennium) Sylvester McCoy was actually quite refreshing. I'd probably put him in at number three.
No idea about the recent (21st century) Doctors, as those haven't gotten across the pond yet.
Btw, on the new ones, do the special effects still suck royally?