I own LOTR and HP and I honestly can't decide which one I like better.
I have to juggle them!
LOTR is aimed towards adults and the book goes into a lot of detail, whereas in the HP books (aimed at a younger audience), something happens everytime you turn the page.
That is my opinion. I think you have to go into each movie at a different point of view. Since a lot of people stay young at heart, they can enjoy Harry Potter as much as LOTR. I know I love them both and am looking forward to the next movies!!!