The LOTR movies are great movies, but are pretty poor adaptations. I don't mind changes which were necessary due to the medium (e.g. cutting Tom Bombadil, which just would bloat the movie without adding anything crucial to the story). But Jackson went beyond that and made changes (for example, having Faramir give in to the temptation of the Ring for a time) because he disagreed with Tolkien's story (that specific change was explained in terms of Faramir's character in the book "doesn't work with the way we are trying to portray the Ring"). That's crossing a line, imo.

The Hobbit movies, on the other hand, are both bad adaptations and bad movies. Truly awful stuff.

I have a lot of criticism for some of the plot changes that jackson made but I'll credit him for this: his films are the first dramatic sword & sorcery type movies that got the tone right and aren't cringe worthy. The previous attempts at LOTR are awful.

Legolas was kind of super in the books, though. I think Faramir was the worst character assassination in the movies.

I think what Tolkien would have hated the most was Aragorn murdering the Mouth of Sauron. Stylistic choices are one thing, but turning morality on its head is on another scale.