The dialogue here the last day or so has been exactly what I was hoping this thread could become eventually. Fantastic stuff, everybody!
As far as my thoughts on the Overstreet: I think they really need to lay out in print their criteria for what is "supernatural, horror, weird, etc." the same way they have for their "scarcity" ratings. ( I might add some books designated as such - scarce, rare, what have you, are sometimes still argueable to say the least. We've been there before.) Basically, I get the feeling they often change stuff to suit their own agendas, whatever those might be.
As for my own opinions, I can totally agree with Pov with the "sci-fi" label for Frankenstein, etc. Technically speaking, they could be classified as such more than Star Wars, which is nothing more than a "space opera." Sometimes though I think that horror wears many hats, and it's putridness oozes into any number of genres. Take Jaws, Alien, Psycho, and the Exorcist for example. All very different vibes, but all with elements easily classifiable as horror.
To me, there is no need for Overstreet to attempt to "break down" horror into sub-categories. Simply put, I'd rather see a reversion to simply "horror."