I am not sure what you standards of 'literature' are since you are just making declarative statements a la 'I think X is much better than Y!' (which is fine in this kind of discussion, I don't expect an actual comparative analysis) but if you simply go by reputation as in 'taken seriously by the literary establishement' then Tolkien and LeGuin are up there, Dick and Gibson are up there, and the others you mentioned aren't. (And MCA isn't up there with them, nor should he be, sorry.)
I'm too old for tl;dr essays, so I'll just go with a quick, shitty subjective.
Good low-brow genre fiction is good, clean, entertaining fun. There's nothing much to it beyond excitement, adventure, maybe a bit of titillation. Classic fantasy example: Conan the Barbarian. (I fucking love Conan the Barbarian, I don't know how many times I've read my Omnibus.)
Good literature goes beyond its ostensible subject matter, and artfully evokes something that is universally human, in a way that has the capacity to awake new thoughts, move, or even change the reader as a human being. Classic example: Crime and Punishment.
So my opinion on whether a book falls under the low-brow genre fiction or actual literature side of the fence is contingent on my opinion on its capability to speak of something outside the bounds of its genre. This is necessarily fuzzy and subjective, since no work of fiction is /completely/ devoid of universal human concerns, otherwise nobody would bother reading it.
Off the top of my head, some sci-fi/fantasy works (books, films, games etc) that by this criterion, in my view fall squarely on the "literature" side of the fence:
- Wolfe, Gene: Book of the New Sun
- Le Guin, Ursula K: Earthsea trilogy
- Avellone, MC: Planescape: Torment
- Scott, Ridley: Blade Runner
- Sturgeon, Theodore: More than Human
- Duncan, Hal: Vellum
- Kubrick, S: A Clockwork Orange
Some sci-fi/fantasy works that straddle the fence:
- Tolkien, J.R.R.: Lord of the Rings, Silmarillion
- Scott Card, Orson: Ender's Game
- Heinlein, Robert: Citizen of the Galaxy
- Kubrick, S: 2001: A Space Odyssey
Some sci-fi/fantasy works that are good low-brow genre fiction:
- Howard, Robert E: Conan the Barbarian stories
- Leiber, Fritz: the Swords cycle
- Moorcock, Michael: the Eternal Champion cycle
- Lovecraft, H.P.: At the Mountains of Madness, The Colour Out Of Space and a bunch of others
- Reynolds, Alastair: pretty much everything
- Miéville, China: pretty much everything
- Banks, Iain M: pretty much everything
- Lucas, Robert: Star Wars (IV-VI)
- Erikson, Steven: The Malazan series
- Corey, James S.A.: The Expanse series
- Asimov, Isaac: Foundation, Foundation and Empire, Second Foundation
Some famous and highly-regarded sci-fi/fantasy authors that are garbage even work as escapist fiction, mostly going to show how low the standards of the genre are:
- Vance, Jack (everything, he just can't write for shit and his ideas are dumb as well)
- Asimov, Isaac (everything other than the original Foundation trilogy)
- Clarke, Arthur C (everything except 2001: A Space Odyssey where he had a good collaborator)
- Leckie, Ann (everything)
- (jesus this would be a long list, most sci-fi/fantasy is utter rubbish)
---> I think Raymond Chandler pointed out that the average detective story isn't actually any worse than the average novel, the difference being that the average novel never gets published. This is true for all genre fiction.