If we truly want to identify a precursor to Tolkien's Middle-earth then we might want to look at something like his translation of "Beowulf" or other literary works that inspired him.
There was no mention of ''literary works'' anywhere. Wouldn't that be the point?
You're right, but that makes the question as phrased even worse, even nonsensical: ''Which is the best movie trilogy? The precursor to Tolkien's universe or the saga which introduced us to the story of Bilbo?"
precursor n. Somebody or something that comes before, and is often considered to lead to the development of another person or thing.
What movie trilogy could be called a precursor to the Peter Jackson films?