Classical Aspects

Recently, I've been doing a bit of thinking and a lot of reading (shocking, I know) and I've come to realize that there is something about literature that I'm having trouble pinning down. It's an old question, but I don't think it's ever been answered to my satisfaction.
Put simply: what makes a work of literature a classic?

The thoughts that dragged me back (because I've been here before) to this ever-pervasive question (especially in my field) follow.
We have classic works of literature, and, by and large, anyone even remotely familiar with a high school English class can identify at least a few of them. Jane Eyre, Moby Dick, Great Expectations, Pride and Prejudice, Wuthering Heights, Mrs. Dalloway, Middlemarch, Oliver Twist, Crime and Punishment, The Scarlet Letter, Ivanhoe, Vanity Fair... and so on and so forth. (Authors as follows: Charlotte Bronte, Herman Melville, Charles Dickens, Jane Austen, Emily Bronte, Virginia Woolf, George Eliot, Dickens again, Fyodor Dostoyevsky, Nathaniel Hawthorne, Walter Scott, William Makepeace Thackery.) And those are just novels. Chaucer, T.S. Eliot, Tennyson, Blake, Byron, Yeats, Keats, Pound, Spenser, Milton, Browning, Barrett Browning, Wordsworth, Longfellow, Whitman, Stein... well, we've got poets coming out of our ears, too. Not to mention playwrights like Wilde, Shakespeare, Marlowe...
But why them? And why do we know their names any better than those of H.D., Mina Loy, Jones Very, Sarah Morton, Adah Menken, William Hill Brown, Charles Brockden Brown, Ellen Glasgow, and so on?
Proliferation doesn't make sense. Nor does lifetime fame. Jones Very wrote constantly. Admittedly, he thought he was the Second Coming of Christ, but you'd think that would add to his interest. Sarah Morton was the most famous American poetess during her lifetime. Associates? H.D. and Djuna Barnes were colleagues (and, in H.D.'s case, a suspected lover) of Pound, Eliot, Lawrence, and co. How well they were liked? Well, okay, so Dickens and Melville had some big hits. Tennyson was poet laureate of England. But. Mellville's books (pretty much other than Moby Dick) flopped. Scott and Dickens both understood the pressure of having to write to eat. Whitman was ostracized from society. The Brownings were actually exiled. Milton, for all his fame, went blind in a closet. Wilde was sent to prison in France.
That said, do you really think Stephen King (yes, Beth, I know) or Dean Koontz is going to be the next Melville or Dickens? I'm sorry, folks, but Tom Clancy isn't ever going to appear on a course syllabus. Nor are Danielle Steel and John Grisham (though, honestly, he'd go on before some). Oprah's Book Club will not be - in all likelihood - producing many great literary giants (Toni Morrison aside). But they are popular.
So what makes literature worth study?
And, to go off a bit on another path, does study necessarily preclude enjoyment? (Because I know some of you are groaning and saying that it has to be dull or intellectual.) To be honest, I enjoy Austen. I enjoy the Brontes. I even enjoy Hawthorne and Dickens. I could do without Spenser, Milton, Faulkner, and Melville, quite happily, most of the time. But I can see the merit in studying all of them (even if I don't personally want to do it).
But. I also see merit in studying genre fiction - the sensationalist kind of literature that Wuthering Heights, Northanger Abbey, The Mystery of Udolpho, and The Turn of the Screw were at one time. Ghost stories (like Beloved, if you want something more contemporary), romances (Pride and Prejudice, Sense and Sensibility, Jane Eyre), and yes, even science fiction (hell, I'm teaching Good Omens - Terry Pratchett and Neil Gaiman - in the fall), all have - when written by the right people - literary value.
Fortunately - I think - these are beginning to emerge in academia - courses on Bradbury, Tolkien, gothic fiction, Agatha Christe, detective fiction.
Then again, I'm a big fan of thinking while you read; I think people should learn while they enjoy something - whether it is learning something about the world, society, or themselves, but, to quote (or perhaps misquote) Einstein, "the important thing is to never stop questioning."