Another big fan of scores here!
Restricting myself only to those not yet mentioned, I think "Back to the Future" is probably top. Oh, and I very much enjoyed Giacchino's score for "Rogue One" - close enough to Williams to sound 'right' and yet also different enough to be its own thing. Oh, and while I really didn't care for the film, the new "Masters of the Universe" has surprisingly good music.
The "Superman" theme is my all-time favourite piece of music, but alas I don't feel the score as a whole hits the same level.
Of the scores that have been mentioned, "Star Wars", "Lord of the Rings", "The Wrath of Khan", and "Jurassic Park" would probably be top. (I've also been listening to the new version of the "Transformers: the Movie" soundtrack a lot recently, which isn't a score but is in the thread.)