Been watching the original LOTR trilogy lately. In my opinion, the greatest cinematic achievement of the 21st century (so far).
One thing I noticed is that Peter Jackson didn't dumb down the dialogue for the audience, at least compared to more recent films.
Consider lines like these:
"I now go to the halls of my ancestors, in whose mighty company I shall not be ashamed" (Theoden on his deathbed)
"Have you ever seen it Aragorn? The White Tower of Ecthelion, glimmering like a spike of pearl and silver, its banners caught in the morning breeze... One day our paths will lead us there, and the Tower Guard will take up the call - the Lords of Gondor have returned!" (Boromir talking about Minas Tirith).
The type of language you would see in Beowulf or Shakespeare, and said with complete sincerity. No snark, sarcasm, post-modern self-consciousness or attempts to turn everything into a witty one-liner.
I think Jackson stayed as true as he could to the source material while still making a mass market movie for a 21st century audience.