I don't disagree with what you say. I was awestruck when I first discovered Star Trek II at the impressionable age of 18. Williams and Goldsmith started my love affair with film music...Horner solidified it permanently.
My concern---which is shared by many---is that Horner often takes pieces of music that have a solid identity with another film, and does a cut and paste job without regard for what the music has come to represent. In essence, he's stripping the film he's scoring of its unique identity. Can you imagine Williams using his theme from Jaws---or one of his most striking motifs from Star Wars---and plastering it into Saving Private Ryan or Rosewood? What if he took a direct passage from "Battle in the Snow" (from The Empire Strikes Back) and stuck it into a battle scene in The Patriot? People would wonder if he had lapsed into Alzheimer's.
I cherish Horner's work when he stretches himself. I understand that every note can't be original. But there are definitely some high-profile motifs associated with other movies that shouldn't be recycled verbatum.