People just love the relationship between Sherlock and John. They’re both very self-aware and affectionate, but also very truthful with one another. There are a really complementary team. John humanises Sherlock, and Sherlock gives John a shot of adrenaline and adventure and the chance to live a life less ordinary. That’s a very potent combination. The relationship with John draws Sherlock back to the human realm, from which he has been distanced for a big portion of his life. It makes him a better detective and a better human being. I don’t mean that Sherlock is suddenly interested in holding babies or eating frozen yoghurt. The great gift that Watson gives him is to make him more human. And if you’re a better human being, the more likely you are to empathise and therefore be a more skillful detective.
— Benedict Cumberbatch, The Independent (x) 29.12.2016