I have a theory, the current doctor when you started watching is your favorite doctor. Would this apply to you?
I started watching Dr who when the reboot was 3 seasons in, I think David Tennant was the greatest doctor. A few years later I finally got wife to give it a shot as I started a fresh rewatch in preparation for Matt Smith's second season, she was ok with Eccelston and Tennant but Matt Smith is far and away her favorite doctor. Does this pattern hold true for any other Dr fans?
Tom Baker was my first and remains my favorite, so much so I actually cried when he appeared as the curator. For me it was a really emotional moment, stupid I know but it was like a direct road back to my childhood which for me , luckily was a largely happy time.
I think this applies to a lot of people, but I don't like to pick a favourite, especially after listening to Big Finish stuff, coz each Doctor has their own quirks and whenever I try and settle on a choice, I get conflicted. If you forced me to pick thought I would say 4