People on the boards only started talking about Fassbender once he played Magneto, and in the case of Cumberpatch, when he was cast in the Hobbit and Star Trek. It is the same deal. His Sherlock show had first broadcast a year before people started talking about him on the boards. Once he was cast in the Hobbit and ST, his name started popping up everywhere.
I think what he means is that it was the Batman casting that made people aware of him, when in fact he had been acting for years before that. The fact that you have cited that Bronson was a limited release backs up that observation.
He is also implying that there are other great actors out there who are just as good, who are not talked about so much on the boards, because they are not in an upcoming superhero film/Nolan film.
I don't think he's being elitist, I think he is bemoaning the fact that there is probably a great young actor out there right now who no-one is checking out, but will happily do so a few years hence, when they are cast in a Nolan film/superhero film.
ie If people are all about the art and not the latest hot thing, they should be checking out the more obscure films.
edit: and by that same token, there is probably some actor who is just as good, who won't get such a popular gig, and as a result their skills will pass by almost uncommented on.
