I just came across this Jonathan Last critique of Return of the King: The End of the Ring. In it Last compares the third installment of the trilogy to the first two and finds it wanting:

WITH "RETURN OF THE KING" Jackson's juggling act falls apart and the chainsaws which he had kept so nimbly under control gouge and mar his final chapter . . . IRONICALLY, Jackson's biggest failing this time out comes in the area of his greatest strength: pacing. The script has trouble with compression, compacting days into minutes without adequately portraying the passage of time. The story, which takes place over several weeks, plays as if it spans just a day or three and involves much wasted motion . . . The script has characters hurtling from point to point, battle to battle, conclusion to conclusion, so rapidly that it's both exhausting and numbing.

While I think Last makes some valid points, I think he misses the forest for the trees. I think Jonah was more on target:

I guess my problem is that I really don't see the Lord of the Rings series as a trilogy in the first place. I'm on solid footing when I say this because neither did J. R. R. Tolkien (cue crazed-fan crowd roar), nor did Peter Jackson (cue slightly less crazed, but still disturbing, roar). The Lord of the Rings was written as one book - with two fingers, banged on a typewriter for half a million words - and the publisher insisted it be cut into three parts. For various reasons - technical, emotional, financial - Jackson emulated Tolkien and shot the whole film in one giant piece. In other words, this is a ten-hour movie.

If you try and look a the movies totally independent of each other I think you miss something. I agree that the first movie was the best as a conventional movie. The action and plot were the tightest. Fellowship of the Ring simply pulled you along. It's action scenes were focused on individuals; they were close and intense.

But Return of the King was never going to be that kind of movie. No one was on the run, the impulse was not fear and adventure but stoic resolve with a strong sense of tragedy. The issues were bigger and the battles more epic in nature. This was a clash of civilizations.

ROK was also a more visual and aesthetic film. David Edelstein at Slate saw this:

Of all the things to love about The Return of the King, it's those lightning shifts in scale that I find the most thrilling. I don't mean just the sudden impossible hugeness of it - those hundreds of thousands of demonic Orcs led by massive trolls and winged dragons called Fell Beasts and eight-story elephants called Mumakil as they surge toward a seven-tiered city that soars into the sky. I mean the way Jackson cuts from that amazing vision to something small: a spiked wheel grinding as the heavy gates of the city close; then a human face - Pippin, say, with his mouth grimly set and his eyes shocked open; then a few hundred thousand more marauding Orcs. So you get eye-popping spectacle, then a close-up with texture and weight, then a flash of human emotion, then more eye-popping spectacle. The threads are awesome, but it's the weave - of the epic and the intimate, the airy and the visceral, the lofty and the blood-curdling - that's spellbinding.