The Lord of the Rings and A Game of Thrones seem like they bear comparison. They both have cultures that rely on swords and horses. They both have learned sages and wicked rulers, strange creatures and fantastic architecture. They both engross and require pause from their readers.
But they really don't have anything in common. They do such different things that they belong to two different worlds. And these worlds are further apart than Middle Earth and Westeros could ever be.
[I'll refer to these two works as LOTR and AGOT even though the latter is more properly ASOIAF.]
My main point here is: AGOT is Daniel Defoe and Stendhal and Hemingway. LOTR is Joyce and Pynchon and Woolf. AGOT is hyper-modern; LOTR is post-modern. AGOT is our world with additions. LOTR is another world all together. The difference between the two works is the difference between realist novels and modernist literature.
Any argument about these two works really depends upon the purpose to which this literature is put. AGOT is a realist novel and fantasy literature. LOTR is faerie, that is, a constructed form of modernism that rejects the realist novel. AGOT is realist in that the narrator is the traditional, modern third-person narrator; there are chapters that are written in the first-person but these are the exception. LOTR is a "found manuscript." It is written by two characters in the book. It is translated into English. It is a fragment of a larger story.
The things that AGOT has in spades are conventions of the realist novel: characters we can identify with motives that we share. Even if we may never stare into the Dothraki Sea or go north of the Wall, we breathe the same air as the characters who do.
Faerie does things differently. It does not give us extensions of ourselves but grotesque and utterly strange forms that make sense only in that other world. Trees that have names identical to their deeds. Halflings identical to us except for the furry feet. And the tough hides. This is not our world. If it is, it is the world utterly changed. It is Charles Dickens's famous moment. Sitting in a coffee-room, he saw the sign outside and read it backwards: MOOREEFFOC. Transfixed, he was homeless and alien. He saw everything anew. AGOT does none of this -- indeed, no realist novel does this. It merely adds to what we already experience, perhaps a richer set of actions, a deeper set of motives, a bit more psychology.
It may seem that these features -- the fallen and fractured human beings, the mixed motives, and the full range of human experience -- means that AGOT is somehow closer to us, that the world of hobbits is more "escapist." But, in actuality, these are just features of the realist novel. Westeros should reflect our own world. It gives us ourselves back without change. For all of Martin's innovations in the realist novel, such as the remarkable fluidity of protagonist and antagonist, he remains bound to the kind of negative escapism that does not conjure human possibility. Rather, it endorses a kind of conservative cynicism, accepting the situation as we see it. Or at least how some of us see things. Life is horrid and anyone may die.
Faerie and modernism generally does not accept the novel to be a simple reflection of ourselves. Whether it is Joyce or Tolkien, what others call escapism in LOTR is not flight but rather the creative exploration of possibility -- science fiction may also join this kind of liberative fiction, as can the more powerful detective fiction. These writers touch the edge of what is possible, they break what is expected. Realist novels can scandalize and transgress, to be sure, but they maintain a basic pact with the world. This contract they will never breach: that the world is sealed and its possibilities given.
Granted, Martin has not yet finished his books yet. We may find that his bait-and-switch tactics with various protagonists may result in the emergence of a standard plot with one or more of the surviving minor-become-major characters. His elves may come back. His dragons may become terrible and desirable. But if they do, he will have to escape the orbit in which his books have firmly settled, the orbit of the realist novel that is escapist in the most mundane sense.
We deserve a world that expands beyond the possibilities of the present day; we demand more than just what is the bare given to us. And so we need to be able to see beyond conflict and characters and desires. LOTR and AGOT really belong to two completely different worlds and two fundamentally different kinds of literature. AGOT may break some of our vision but things like LOTR can open us up beyond what we could ever see. Whether we need to have that possibility or if we should just rest with what we have is another question.