Just came in here to mention that I’m an outlier: The Twin Towers is my favorite one of the trilogy.
Now, I hadn’t read the books beforehand (did later on), but I did see Fellowship before TTT. Honestly, I was underwhelmed by Fellowship, largely because its ending is so abrupt and flat in isolation. When you don’t know what’s coming next, it didn’t really leave me wanting more.
That said, after I saw TTT, I appreciated Fellowship FAR more than I first did, and now I actually quite like both. Fellowship still meanders, but TTT is more meaningful-- and I still feel that TTT is the most efficient and propulsive of the trilogy. Shit actually happens throughout the whole film.
Plus Helm’s Deep is the best action sequence in the trilogy 
Return of the King, alas, struck me as a mess then, and even more so today. Not only the multiple endings dig-- although that dig is entirely justifiable, the film never knew when to stop. No, it’s just too loud, too flashy, full of “stuff”. The characters stop being interesting and overstay their welcome, IMO. I still feel that ROTK’s Oscar win was a prize for the accomplishments of the trilogy as a whole, but I don’t think anyone would have argued it was a “Best Picture” quality film had the previous two installments not set it up so well.
BUT… Jackson deserved an Oscar for the accomplishment of the trilogy, I agree there.
As for hindsight… effects movies rarely age well (I can’t imagine Avatar will hold up in a year, let alone a decade, once other movies approach and surpass its technical achievements), so we’re left with the core elements of the movie: plot, characters, writing. In hindsight, the LOTR movies don’t appear as strong to me today as they did then.