The way I think of it is “can you hum the tune?” I am pretty well versed in classical music, and for the life of me I could not hum any of the themes in the LOTR trilogy. And I have just watched the whole set again about a month ago.
Star Wars? Yes.
Indiana Jones? Yes.
Superman? Yes.
Baron Munchausen? (just to include non-Williams) Yes.
The Natural? Yes.
Pirates of the Caribbean? Yes.
LOTR? Nope.
To quote Patrick Swayze in Roadhouse “opinions differ”. I think LOTR soundtrack is the best.
1. It is structured like an opera with different themes, e.g The Hobbit Theme, Sarumam’s Theme, Sauron’s theme, the theme of the Elves and of Rohan.
2. The Chorals in different languages, e,g English, Old English, Sindarin, Queyna, Adûnaic, and Neo-Khuzdul.