Except it's not really a trilogy, if by that we mean three sequential but reasonably self-contained stories. Tolkien considered the novel a single work in six books published for convenience as three volumes, and Peter Jackson likewise considers the work essentially one film. That doesn't mean there isn't variation and a creative arc, but even a single film or novel can have that.
I dunno, I still like The Lord of the Rings.
Yeah, that's an excellent point of comparison.
Speaking of which (sort of): SDG, the opening lines in your review (I haven't read the whole thing yet) made me think not of The Empire Strikes Back but of the Godfather series. Many people believed -- and still believe -- that Part II had taken the themes of the original Godfather about as far as they could go, and that Part II had "completed" the story in a very definitive way. So there were all sorts of hurdles that Part III had to overcome when it came out over a decade later, not unlike the hurdles that Toy Story 3 might have had to overcome when it came out over a decade after the second film in its own trilogy.