Really, the three parts of Peter Jackson's trilogy are just one long movie, and I have a hard time separating them. But I have a fondness for 'Fellowship', when the whole gang was together, off on a quest to destroy the Ring. I liked the team interaction, before they got split up. But, of course, the entire trilogy is absolutely epic.
Thousands of comments have been made on this outstanding production and there is little left to write that has not already been written or said. Again, not surprisingly at last night's 'Oscars', the third film in the trilogy took most of the awards. Like others I could give glowing comments about content, acting, production, direction, visual effects etc. but will instead, convey what I consider to be equally important; that is the realistic and accurate portrayal of a classic masterpiece of literature from one of the world's most imaginative authors.
A difficult call, but I found this the best of the three. If you are a fan and can ever find an entire day -- watch all three, extended versions. And, though others sometimes think the following advice I've given is just plain weird, I have advised friends and relatives going through a bad patch and needing a little escape to watch the trilogy. Lets you escape for the day and put your troubles into perspective -- after all, nothing can be as bad as being hunted by orcs.