I haven't seen many episodes of all of them but I have seen at least one episode of each of them.
I would say that the 3rd, 4th, 9th and 10th are the best Doctors, for me.
The third had a great semi-antagonistic relationship to the Brigadier. Also, I liked his humourous situations (He picks the lock on a prison to break out, just as the guards are coming to bring him before their boss. His response, to say "Oh, how embarassing!" and trying to close the door again).
The fourth was funny, and also had some nice social commentary lines - the planet's civil war that destroyed almost all life on it, that took 6 minutes, and he looks sad and says "...that long." And he had iconic traits that people remember even today...K-9, "would you like a jelly baby", the long scarf.
The 9th and 10th are also good, and I enjoyed watching both of them. It is a different style than before, but if we are talking about doctors I like, well, I like both of them too.
The 5th and 6th doctors didn't do it for me. 7th was ok. 8th was "what the




was that?". I only have seen the very first one ever with the 1st doctor, and to me he just came off as a bastard (which was interesting, but not very "doctor"ish as I had come to understand and like the doctor). The second I have only seen one episode of (well, that and the three doctors), and well, he did not seem Great, but merely good.
I would pay money to somehow get a "the four doctors" with the 3rd, 4th, 9th and 10th, but I don't even know if 3rd and 4th are alive, and if they are, they likely are too old for the roles.