In the history of film criticism, the western holds a special place. The western really is the start of "genre criticism" in film — that is, that variety of analysis and interpretation that foregrounds audience expectations created by the way a film's narrative and thematic elements resemble other, similar films.
Because there were so many westerns made during the silent era and the first decades of sound film (up through the 1960s), these formal — or formulaic — similarities became readily apparent from film to film. Indeed, it was around the 1960s — when westerns started to be made less frequently — that "genre critics" would use westerns as a kind of starting point for talking about genre itself.