I've been reading this whole thread and I don't know where exactly to insert this comment, so I'll just stick it here.
Tolkien himself one wrote a commentary somewhere - I can't recall at the moment - which sheds a little bit of light on a mystery of literature which has puzzled me since high school. That mystery is, why is it that all "great literature" is judged solely on it's metaphorical, allegorical, or other such misinterpretable details? (A similar question is, why is the "best" artwork the most unusual abstract stuff that nobody can make any sense of?)
The commentary which Tolkien wrote, I recall was taken from his memoirs or some such - I was just skimming through some book in a bookstore and saw this and remembered it ever since. At the time Tolkien was writing this, he was terrified that his favorite type of writing was going extinct, being exterminated by the prevelance of what hits most best-seller lists nowadays - melodrama, tales of ordinary people in their ordinary lives in real cities at real times doing things that may as well just be historical accounts of things tha tnever really happened.
The writing that Tolkien loved was what we now call fantasy stories, including most scifi - tales of fictional worlds meant more as an act of sheer creation, a separate universe for the reader to visit and explore, and not necessarily intended to be any sort of commentary on the real world at all.
This is my favorite type of writing as well: and two of my three favorite authors, Tolkien and Asimov, are my favorites because they are renowned not just for creating a bunch of little fictional pocket-worlds, one for each book or novella, but for creating and maintaining INSANELY HUGE fictional universes. The skill and ability to do so with any degree of self-consistancy, especially over an entire career, is not a skill to be undervalued, and one that I have found very few people have. That's possibly because it' is undervalued, or perhaps it's undervalued because most people can't relate to it. "So you can tell me in detail how many grains of sand are in any given inch of any of 500 different nonexistant planets? So freaking what, where's the sex?"
An analogy I can think of is architecture. When someone builds a house, do they build it to make people think over it's symbolism, how it's shape can be interpreted to shed light on the story of human existance, and how people can learn from the arrangement of hallways and rooms? No. A house it built, besides it's simple functional needs, to be - for lack of a better word - COOL. It's an enjoyable place to simply BE. A retreat, an escape, a little world of it's own, built and designed solely to invoke an enjoyable or at least interesting mood and please the occupant. Likewise with a lot of fantasy.
Now this is not to undervalue character development and all the good stuff that lit professors preach about; merely to value the skill required and the enjoyment gained from creating virtual realites solely through text. For the same reason that some might criticize much of fantasy for lacking depth in it's characters or theme, I criticise much of the rest of literature for it's utter lack of creativity in the worlds in which they place their stories. TRUELY good literature requires both, which is why I'd have to say Orson Scott Card is my favorite author of all time. Not only do many of his stories - such as Ender's universe - take place inside a vast fictional spacescape which is entirely self-consistent and full of many original concepts, but reading some parts of them honestly made me cry.
