Sort of. Originally the term was coined and embraced by actual Speculative Fiction/Science Fiction writers,
the wikipedia entry here has a fairly decent and accurate history of the term. Academia, scholars, the amateur critics in fandom, and writers of genre are more likely to use the term than the publishers themselves. So I wouldn't define it as a marketing term exactly. Personally I see it more as a label of convenience that brings together fantasy, Sci-fi, horror (anything in opposition to realism) for critics and fans to discuss genre works.
This terms becomes problematic in the way I just used it as an overarching genre that is in opposition to realism when applied to horror for some of the reasons you hinted at. After all, horror might be about a psycho-deranged serial killer (something that can happen in real life) and have no fantastical elements like a ghost or a demon-clown.
Also, it's not rocket science to find decent genre work. Pretty much read the Classics. LeGuin, Asimov, Delaney, Ellison, Dick, Gibson, Wells, Butler, Herbert, etc. Read "Best of" lists put together by fans, critics, and writers (then compare to see what titles appear on multiple lists), flip through critical reviews, read more traditional reviews, see what people are writing and talking about in fandom.
I generally don't have to spend too much time wading through crap (at least how I would define crap. As they say your milage may vary) because I already know which writers and which books by them are worth checking out, plus if I want some newer writers I already have a list of people whose viewpoints I trust.
As far as too few speculative fiction works appearing in literary circles? Define a literary circle! Are you speaking about the mainstream of academia? Then fine, that's probably true.
There is a whole community of scholars who publish on speculative fiction (since there are at least five Peer-reviewed scholarly journals focusing strictly on those genres), who teach Science Fiction, Fantasy, or Horror courses in academia, and still have a traditional background in a more "acceptable" area of expertise.
