I don't like terms like "real literature". I would say the Foundation series despite its weaknesses is worth reading for anyone who wants to be well rounded in his/her book choices.
* Taught by mainstream college professors
* Well received by mainstream literary critics
* Winner of a notable, mainstream literary award
* Will be found on the desk of a character in several movies to indicate the character is of above average intelligence
I guess that's why I'm hesitant to use term like "real literature". I'm very picky about what I read, that is I tend to stick to books like those you described. On the other hand I don't like to appear that I read those books just so I can name drop or look smart when someone sees my bookshelf.
Snow Crash has a bitmap pattern that can hack into programmers’ brains and knock them unconscious and the complete collapse of nation-states and The Diamond Age has pervasive nanotechnology. Dune has gigantic sand worms and psycho telepaths. China Miéville’s books have giant mutant bird-people. Speaker for the Dead includes aliens, artificial superintelligence, faster-than-light communication. &c. &c. &c.
“Real literature” (any way you define it) has many of the same building-blocks: gods (The Illiad), fairies (Twelfth Night), voyages through the underworld (Dante’s Inferno), characters who hop from one body to another (Death in Venice), interesting new interpretations of language and cognition and radically different cultural/social customs, etc. etc.
But works (including those set in space) that oversimplify and preach at us, or just serve as fantasies for us to insert ourselves into as passive escapism are little better than Horatio Alger novels, or, say, the trashiest kinds of romances. They can be fun, but ultimately they don't have quite so much staying power.
I think in creating a new voice (that of the AIs), Bungie used an entirely new mode of expression, with brilliant results (I bet the Marathon's Story website is still active). The story, by the way, is relatively far removed from the present day.
Interestingly, I find that Dick tends to borrow from the pulp stuff a lot. He's a pulp writer--but he distills the best out of it.
"Fiction" is a radically constrained subset of "science fiction".
One of the reasons I enjoy science fiction so much is that in the hands of a master, it has much more possibility to be truly powerful and good literature than the genres that limit themselves. Like any other ingredient, it can either make the dish or ruin it, but the ingredient should not be judged by the ruined dishes people make with it.
(Example: I recommend A Deepness in the Sky for an interesting literary treatment on slavery that goes well beyond "Slavery is bad, mm'kay?" and with relevance well beyond the usual historical issues. Try it in non-sci-fi and it would either fail or be silly.)