又看到一篇SPN角色分析觉得写得好棒让我把它记下来
in response to this:

First of all kudos for the url...
The idea was that the story was ~about the two brothers~, which I suppose would share screentime in a fairly balanced manner, but Sam was intended to the the point-of-view character, the “filter” we would experience the story through.
It makes sense on paper: Sam is a character in a situation we can relate to (college student living a regular life), whom something happens to we can sympathize with (he loses his girlfriend tragically) and who - while he knows about that world having grown up in it - has distanced himself from the world of the supernatural, so we, the audience, who enter into that world for the first time as we watch the show, “enter” that world together with Sam as he re-enters it.
Dean, on the other hand, is a character who’s always been in that world, so he can’t be our “guide” into entering it. He also has a lifestyle we can’t really relate to, because the audience in front of the tv is obviously closer to the college guy than the rebellious nomadic monster-killer. He doesn’t have attachments other than to this mysterious missing dad, and is a generally mysterious person himself, so Dean is sort of an object to discover and decode rather than a subject to identify with.
Enter Jensen Ackles and Dean is suddenly a magnetic character who exudes a vulnerability that people can, indeed, relate to.
Enter Sera Gamble, Raelle Tucker, and John Shiban (I’d say the authors who most explored Dean in s1) and they do write Dean in a way that’s interesting and touching.
(Sera Gamble is a weird case, because she can do utter disasters but also write really good things, one could argue she’s the one person who most drove Supernatural from Kripke’s original idea to what we actually got, she’s the one who most drove the story away from ‘urban legends’ to religious themes & co, and while I haven’t seen the Magicians I know that she’s both the person who built a very interesting story and destroyed it.)
Dean and Jensen have carried the show all along both because Dean ended up a more compelling character and also because Dean has the strongest (narratively and emotionally) relationships. All the most interesting side characters have relationships with Dean, with a few exceptions (and again if a side character has a relationship with Sam, their exchanges with Dean are still more interesting, just think of Ruby!).
Crowley was supposed to be “associated” to Sam in the Carver era, to balance Dean’s association to Cas (s7 ends with Crowley making a cruel speech to Sam, the scene in the church where Sam almost turns Crowley human, Rowena using Sam to kill Crowley...) but Crowley ends up having a massive arc with Dean and a love triangle with Dean and Cas, which is why the Carver era is so unbalanced towards Dean XD (Then the writers did their best to make Rowena a “Sam character”, but at that point she was quite her own character with her story with Crowley and all, so it wasn’t really a narrative-supporting arc.)
Mary was both Dean’s and Sam’s mother, but her relationship is with Dean. Jack was presumably supposed to be associated to Sam more, too, with Sam taking him under his wing while Cas is dead and Dean blames Jack for it, but the relationship between Dean and Jack is the one that immediately stands out and gets developed.
One of the most unrealistic thing about the show is having all the side characters talk about “SamandDean” “the Winchesters” all the time when what they actually mean is “Dean and his brother”, if not just “Dean” at all.