This is strictly applies to the AG companions.
Everyone has their favorite and least favorite companions, and usually come down hard on Rose. I get it, one of our favorite things about the Doctor is that he is not only smart and inquisitive, but that he has the wisdom of an old man in the body of a young man with the heart of a child. I love when he acts like a kid and gets into trouble; I love how he interacts with the world and sees it through the lens of childlike trust and curiosity. And his personality comes out best when he’s interacting with the companions. With Rose, it felt like you didn’t get that, but I think my observation may have something to offer as far as reasoning behind companion likeability.
Martha: When the Doctor traveled with Martha, I felt like he could be his carefree self. He was energetic and excited and curious, but also oblivious to her feelings. The fact that he was being the version of himself that I love, but that I liked Martha and Martha was hurt by his naivety, made me uncomfortable. I want to completely immerse myself in episode and go on that ride with the Doctor, not check my feelings because another character is spurned.
Donna: When the Doctor was with Donna, he was able to completely be himself. She didn’t care if he didn’t notice her or if he looked twice at River Song. She was a good friend and let him be who he was and who he needed to be so I was able to enjoy the Doctor without feeling like he was insensitive.
Amy: The Doctor with Amy, not with Rory, was awesome! He was able to be himself, his newly regenerated self. She was young and vibrant, like the new him. And I really liked their chemistry and blossoming friendship. Where Donna let him be himself, Amy helped him be himself by taking care of him.
Amy/Rory: When Rory was in the picture it was a different story. Together, at first at least, it was a bit like with Martha. I wanted to enjoy Amy and the Doctor’s friendship, not worry about how it made Rory feel. I would get totally caught up in how Amy was coming along as a companion and then be like ‘oh, that must be uncomfortable for Rory.’ Luckily, they resolved that when Amy and Rory got married and started their own life separately. Together, they enhanced the Doctor’s childlike qualities by acting as the adults so he is free to do other things.
Clara : I have only seen up to season 7 but I think that Clara let the Doctor be himself too. She was obviously smitten with him, which she didn’t really try to hide, but she didn’t pressure him into romantic situations, which felt much less restrictive.
Now…. ROSE: We can’t look at Rose through the same lens because she didn’t have the same doctor! The ninth doctor was hurt, guilty, and wounded. He wasn’t as carefree, he was always a bit burdened. Of COURSE they developed a deep, intimate relationship; that’s what he needed at the time. Rose was shocked when he regenerated because he became a whole other person but she didn’t know a carefree man like the others, she feel in love with someone who was openly flawed and lonely.
