Mortimer Adler, in his classic "How to Read a Book," suggested five questions to help readers evaluate the artistic quality of a novel (and I quote):
1. To what degree does the work have unity?
2. How great is the complexity of parts and elements which that unity embraces and organizes?
3. Is it a likely story, that is, does it have the inherent plausibility of poetic truth?
4. Does it elevate you from the ordinary semiconsciousness of daily life to the clarity of intense wakefulness, by stirring your emotions and filling your imagination?
5. Does it create a new world into which you are drawn and wherein you seem to live with the illusion that you are seeing life steadily and whole?
He writes, “I will not defend these questions beyond saying that the more they can be answered affirmatively, the more likely it is that the book in question is a great work of art. I think they will help you to discriminate between good and bad fiction, as well as to become more articulate in explaining your likes and dislikes.”
Adler says nothing about fantasy fiction (why would he, writing in 1940?). But his questions four and five would suggest, as J.R.R. Tolkien claimed, that fantasy done well can be one of the highest forms of literary art, bar none. (Of course, where it fails, it can also be among the worst.) In fact, Adler’s questions might even suggest that “literary” fiction succeeds only insofar as it approximates what Tolkien called “subcreation”—a thing at which the best of fantasy excels.
After all, what kind of imaginative writing better “elevates you from the ordinary semiconsciousness of daily life,” especially “to the clarity of intense wakefulness,” than the kind that takes you out of our own world to another realm? For it to achieve this elevation, though, the writer's craft has to have that same intense wakefulness about it. It can't be a sleepy hodge-podge of worn tropes, but must select its detail with precision. The best fantasy does this as well as any kind of writing.
For that matter, what kind of fiction creates “a new world into which you are drawn and wherein you seem to live” more completely than the kind that requires “subcreation” of a world in the author’s imagination?
In fact, done well, fantasy can also excel at what Adler calls the “inherent plausibility of poetic truth.” Not factual truth, of course—which isn’t the point of fiction, after all—but the truth that is deeper than factuality, that touches the soul.
Needless to say, “literary” fiction (perhaps better termed “realism” fiction, in this conversation) can attain to high art. Honed language and clarity of thought and expression can bring us into an alternate version of our own world, in which none of the fanciful elements (like magic, or strange geography, or otherworldly creatures) plays a part. This alternate world is so like ours that the reader has no need to learn special rules, except those of the writer's peculiar point of view. But it is, as the life of an imaginary person living in an imaginary society (albeit one very like ours), an instance of "subcreation." It simply doesn't go as far in the process of subcreation as fantasy does. Or maybe we should say that it cloaks its subcreation more intentionally than does fantasy.
Meanwhile, fantasy, rather than cloaking its imaginative work, tends to cloak the similarities that exist between its imagined world and our own.
Both, then--the "realism" fiction and the "fantasy" sort--have the power to bring us out of semi-consciousness to a wakeful state, a new recognition of the world in which we live.
And so, a work in either genre can be termed "a great work of art." At least in Adler's way of defining it.