Oh yeah, there was a poll too...
Voted Harry Potter. As a writer, I appreciate the clever and thorough way those books are written, compared to LotR. Haven't read Narnia, can't find them in the library.
As for Dune, I definitely liked the first one. It was sort of magic, there was some sort of dreamlike state all through it. You join the adventure at once, without knowing what a Heighliner or the CHOAM is.
The Preludes explain all these things very closely. While I read them, I liked that, but looking back at it, it made them spoil and take the mystery away from Dune. The Preludes are far too down-to-earth written for my liking.
As for the Butlerian Jihad, I got a little sick while reading it. I found these guys' (the writers') obsession with blood and guts outright nauseating.