I can see why the Fourth Doctor is the most popular doctor of the classic series and I do like him a lot, but the third doctor is my favorite so far. Also, he and Jo Grant are the only doctor/companion pairing that I actually ship romantically. Not ten/rose, not fourth/sarah jane, not twelve/clara, just third/jo grant. I've never cared much for ships in Doctor Who so the fact that I ship these two is saying something. And I know their affection is meant to be purely platonic in canon but I think they have really good chemistry and are cute together. Also I love age gaps so that adds to it.
Third and Jo are just overall super fun characters and their connection is super sweet and genuine. I love Fourth and Sarah Jane but I miss them a lot.