I agree about the way the movies are (I say are, not 'may') affecting our interpretations of Tolkien's work. I suspect the effect is very subtle for many of us, but images stay in the mind & are more easily accesible than our long, complex, deeply reasoned ideas. I am glad for some changes though - principally the events at the Sammath Naur, which are totally different in the movie to the way they are in the book - Frodo's brokeness & Gollum's exaltation & his fall which results from it, rather than from a struggle with Frodo as in the movie. Personally I would have hated the film if they'd given away the 'true' story. I think that should remain for the book, for those readers who follow Frodo's story right through to that point.
I remember reading something by Jung, where he gave a line from the Mass, in Latin, but refused to translate it, as he felt it was too 'sacred' (even though anyone with an English-Latin dictionary could have translated it for themselves in a few seconds). He felt it should not be given out in a psychology textbook, but left in the context of the Mass. I'm not comparing the two!! But I think the events at the culmination belong in the book only, & I don't think a movie theatre is the place for them to be given away.
I'm fumbling to get across a point here - maybe if you go to this site:
http://home.agh.edu.pl/~evermind/galeria2/galeria2.htm
Look at the image by S.Juchimow - 'Oblaskawienie Smeagola' (2nd row, far right). Maybe it also relates to the Sammath Naur topic too.