Ralph Bakshi, who had a go at filming the trilogy in the 70s, said of his difficulties that "epics tend to drag". That's a true word.
Tolkien isn't a particularly good writer. Fidelity to the books may have been required by the fanbase but proves artistically limiting. An able screenwriter- given their head- could have buffed up the characterization, given the dialgue some zip, eliminated plot holes, removed absurdities. If it had been me I'd have started by knocking Merry and Pippin on the head. And I'd have shortened some of the action sequences in order to find room for Tom Bombadil, Goldberry and the barrow wights.
What does Sauron actually want from life? To turn Middle Earth into a simulacrum of 19th century Stoke-on-Trent? But even the grimmest 19th century industrialists didn't actually want to live in the hell holes they created. They built their factories, drew the income, retired to castles in Scotland.
And Hitler- so far as we know- never so much as visited the death camps. He built himself a place in the mountains, surrounded by lovely views.
True epic- Gilgamesh for instance or the Iliad- is pre-Christian and doesn't play at goodies and baddies. Its moral complexity makes it the fore-runner not of modern epic (eg Tolkien) but of the 19th century psychological novel.
Frodo is dull; there's no humour to him, no quirks. He just suffers a lot- like Little Nell. Merry and Pippin are that dire thing- a comedy double act which faisl to amuse. Sam is the perfect batman as seen de haut by his amused and condescending employer. The actors who play hobbits add nothing to the characters as Tolkien wrote them- which is a missed opportunity.
McKellen has a lovely warm voice- but is one of those old time stage actors who is always visibly and audibly acting. It's a joy to watch Christopher Lee in anything. Same goes for Sean Bean- a very good actor who should have had more opportunities. Viggo Mortensen has presence. Orlando Bloom doesn't. John Rhys-Davies is buried in false hair and prosthetics.
Elves are Victorian angels minus the wings. Solemn, abstracted, humourless. Who'd want to have to play one?
The black riders are Sauron's weapons of mass destruction but keep failing miserably: they fail to sniff out the hobbits when they're under their noses, back off from getting their robes wet at the ferry, fall for an obvious trick at The Prancing Pony and get chased away by Aragorn when it's four against one. This is Tolkien's fault, of course- as many things are *.
One of Tolkien's greatest strengths as a writer- his sense of place- doesn't translate to the screen. The New Zealand landscapes are magnificent, but generic- which Tolkien's never are.
Orc archers- like German soldiers in almost any war film you care to mention- are lousy shots.
I love the whooshy blue world Frodo enters when he puts on the ring.
The ugly-wuglies are beautifully designed.
The ambition is awesome. And so is the achievement. The Lord of the Rings is an unfilmable book but, by golly, Peter Jackson went and filmed it. You can accuse the result of anything but insincerity. So many big, mainstream films are cynical affairs- and this absolutely isn't. The books and the movies stand shoulder to shoulder- cultural artefacts of an equal height and density- long to reign over our imaginations...