I am a Fourth Doctor fan. Probably not a very original choice coming from an American, but it is an honest. There are four reasons the Fourth Doctor is my favorite.
First, my introduction to Doctor Who came from PBS repeats in the mid-80’s and from that short time period the Sci Fi Channel aired the series in the mid ’90’s. Both emphasized the Fourth Doctor’s episodes, so I had seen them before ever watching another Doctor’s adventures. You always remember your first.
Second, the Fourth Doctor was around the longest--seven years. His lengthy stint gave mea good chance to see him duel with all the regular villains like Daleks, Cybermen, and the Master There were also some other memorable villains (Sutehk, Dr. Morbius, and the Robots of Death) and episodes (“City of Death,” “Robot,” and “Talons of Weng Chiang.”) Those count for a lot of fun experiences.
Third, There was a constant gothic horror vibe running through the Fourth Doctor’s adventures that reminded me of Hammer Horror Films, of which I am also a fan.
Finally, the Fourth Doctor had the mot interesting companions. Sarah Jane Smith, Leela, both Romanas--I will even give Adric faint praise considering how significant he woun up being later on when the Fifth Doctor took over. The doctor is only as good as the companions with whom he gets to interact.
I am going to give an honorable mention to the Ninth Doctor. His adventures came right after my health fell apart, ruining every life plan I ever had. He had been broken by the Time War and the loss of his people. The melancholy personality he exhibited throughout his lone season echoed my own. We were both guys who had nothing to live for, but kept on anyway.
We both developed a thing for Billie Piper, too.