The analogy fails for even more than just the narrowly specific setting. Its important to note about the fall of the Western. . .
1. A large part of its disappearance had nothing to do with popularity, but with the rising cost of filming Westerns. Hollywood had, for decades, relied on a preexisting supply of horse trainers, stage cowboys, and other skilled workers who arose from the prior "western show" business ( as well as from the actual cowboy business ). The fact that there were so many such people meant costs were low. When time and demographics kicked ( ie, the workers retired or died ), it became more expensive to film Westerns. And what a coincident, right around that time is when Westerns stopped showing up so much!
2. Even assuming that there are relevant comparisons. . . Westerns were a dominant part of popular culture for at least 40 years. Superheroes aren't even halfway there.
