I"ve read Lord of the Rings and all the Harry Potters. I'd have to go with Harry Potter myself - I know the Lord of the Rings is considered a classic - but ever tried reading it!? It's incredibly boring, it drags on and on and on, and totally over describes everything. And I know heaps of adults who read Harry Potter, I'm bout 20 now, and I started reading them when I was 11, but I got older in between each book, and felt like the book grew with me, prob cos Harry was 11 in the first one. But I still like to go back occasionally and read them for some easy, fun reading.
As for the movies, I guess the Lord of the Rings does a better job, true it cuts out a lot, but I think that's necessary, its still rather entertaining. Whereas the Harry Potter movies are no where near as good as the books, they cut all the "personality" out of it.
Theres my take on things, to each their own though, yeah?