The hierarchy isn't exactly a strong one, but goes somewhat from
- "Scientific bogus - but if it were true we wouldn't know about it"
to
- "Scientific bogus that we can pretty much exclude by only looking out of the window".
The former would be for example time travel, telepathy, Vampires and a lot of classic SF stuff: It's by all objective means bogus. But
yet if they would really exist, they would be pretty hard to find, and are hard to definitely rule out with our current experience.
The latter is alternative Earth scenarios like Transformers fighting in WWII, a whole lot of Anime-realities which are clearly alternate realities of our real universe - and giant space mushrooms on which supersized tardigrades regularly visit our planet and which can be assessed by taking shrooms. While the former takes a level of disbelieve to get into (like accepting demons in Horror movies, or FTL in scifi) - the latter just clearly places the entire construct in the realm of an alternate universe, like a steampunk world or anything. Which can be very interesting in it's own right, but completely falls flat if it's intention is to be a realistic depiction of our own future.