I'm approaching this with the words of non-readers in mind; I have had many (oh so many) conversations about the films with non-readers, and went to see the films with non-readers. One opinion I've heard over and over is that many did not see Sauron as such an enormous threat. I have heard several people say that Saruman was the real 'bad guy' in the films. I have heard, as have so many others, that the films ought to have ended at Mount Doom. This all adds up, to me, to show that in some way PJ
did fail to convey something very important in the films. Now, I thoroughly enjoyed the films (not least of all to pick over the 'wrong' bits

), and I am actually loathe to say this, but I feel that PJ somehow failed to portray the absolute villainy of Sauron.
How? And indeed, Why? For one thing, the image of the 'eye' eventually was degraded into being an image of a
lighthouse; are not lighthouses a symbol of safety to us? Another reason, and one for which you can hold PJ blameless, is that the power of Sauron was entirely psychological; certainly, the power of the ring works on the mind, and PJ did portray this. But as for Sauron's power beyond the ring itself, it is a difficult thing to portray such a power. And to be added to this is the fact that
action was something very much grasped upon, and to portray both, especially in combination with trying to portray all the other multifarious fantastical aspects of Middle Earth, and keep a story going, well, I wouldn't have put money on it being pulled off perfectly.
Now this leads into the
Why. A book can be put aside, a reader can turn back a few pages if they start to wonder if they have 'missed' something, and most importantly, a book can be read at your own pace. A film has none of these benefits, and it must be pitched at a middle ground somewhere along the line. It must, essentially, find a correct pace. And to do
that, it has had to lose something along the way. I think it was
inevitable that some of the essence would be lost.