Low Tech < High Tech
I'm not the biggest fan of reverse-engineering stuff. That is, "a spaceship is a flying boat" or "a scientist is a wizard". It's a very modern way of looking at things, and should be avoided. (Light sabers, for instance, are okay, because they're simply a high-tech version of a very old mythological concept) When medievalizing a modern work, one should think of the Theseus's ship paradox--the more modern (or futuristic) aspects of a work are replaced, the less of that actual work it is.
This also applies to the actual medium itself. Something that exists exclusively as a video game or a Netflix series is less likely to resonate than something that exists in a more solid or low tech format, because it will disappear in a non-industrial world. Essentially, oral
Older < Newer
The best way to know if something will be passed down over time is evidence it already has been. The United States is a very young country, and has a very young culture, but if it's closer to a century than not, it shows potential of staying power. There's also the above mentioned tech aspect where it remains in low tech forms, and that people will understand it more if it's an antiquated setting. Finally, it's more likely storytelling will be done by the village elders, so stories will reflect their memories and interests.
Rural < Urban
90% of people are farmers, and what was once derisively called "Flyover country" now makes up a larger segment of the population. Therefore, material that appeals to Middle Americans, and an even more conservative version of Middle Americans at that, is going to be more well-remembered. Therefore, less stories about antiheroes, more stories about the God-fearing. (The plot of the occasional monster movie is good, though.What better way to keep the youth from fooling around than stories of a Hockey-masked killer?)
Public Domain > Private
It's not that there are copyright lawyers
Real < Fictional
Mythology has always been around, but the idea of fiction for its own sake is relatively new, and kind of uncommon in olden days. Therefore, there's largely going to be a focus on people who actually existed, if sometimes in mythical takes on them.
