I've written a post about Holmes and Watson before, so this one will be rather short because I don't want to just go over every single I've said in the past. I just want to highlight some key details and talk about them, so that we as readers can appreciate them or try to work out why we appreciate/don't appreciate them. Also, so that we who are writers can see if we can apply the same principles and strategies to make our own character relationships as immortal.
First, another snapshot-
Watson, mate, we're going out.
Ugh, Holmes, I'm trying to sleep. But okay.
Watson! The game's afoot!
Yeah, I'm coming, would you just stop being so untidy and erratic already?
Watson! I'm busy with this Really Important Case, so could you head over to this Remote Part of the Country and meet with This Person in Distress and Observe Things For Me? (Of course, though I'm not going to tell you this, I'll probably be lurking there myself, in secret, and you'll suspect me for some time, only to realize it's really me! By which point I'll have solved the case! Hooray!)
Yeah, why not?
If Watson had been a woman, I have no doubt there would be many an outcry today about his devotion to Holmes and Holmes's taking of Watson for granted. However, it must be noted that for all the hilarity in this formula, Watson doesn't just help Holmes for Holmes; he does it for him, yes, but also because he likes it himself. He likes the mystery, he likes the excitement, he likes being put in charge of things, even if it's Holmes who always finds the answers. He enjoys being the chronicler.
So lest anybody think Watson is Holmes's flunky, I have to point out that they need each other equally, and their relationship, for all its appearance, is one of relative equals.
Which, of course, is why it works so well and is still such an appealing relationship. Equals, whatever appearances suggest.
While Watson never refuses Holmes his help, whatever the unnatural hour, it's equally obvious that Holmes needs Watson; Watson is the only one he trusts and relies on. There's also a wonderful scene in the story of the three Garridebs, where Watson is shot and Holmes's reaction gives Watson - and the reader - all the satisfaction we need.
As I see it, and bear in mind this is just me, I think characters need to be equals for their relationship to really stick with us or mean something to us. Sure, the power's got to shift from one to the other in a story. This is for drama, for tension, for conflict. But ultimately they must be equals - in the reader's eyes, in other characters' eyes, in each other's eyes - for it to work. They must be worthy of each other for it to be a relationship or love story that a reader can get invested in.