Let me say this, I HAVE read the HP books, at least that is, up to book 5. After I read Order of the Phoenix I decided not to read HP anymore. It got too dark and creepy for me. I was upset over the death of one of my favorite characters, and I saw how deep it went into the world of witchcraft and the occult, I mean the whole story is about a school teaching magic and witchcraft. No where is god ever mentioned in the books.
To compare Harry Potter with Lord of the Rings, Lord of the Rings has other characters besides wizards, the magic is not discussed in great detail, it is something that just happens, and Lord of the Rings is more of a fantasy epic, something like King Arthur or Beowulf.
As for Narnia, it is a children's story, and there is the evil white witch, who is evil and uses her magic for evil since she is bad, she is punished with death at the end of the story and the harm she did is undone by the good mighty lion Aslan, who represents Jesus, the 'lion of Judah.' In the magician's nephew, the supposed "magician" learns his lesson in dabbling with magic the occult and the arcane and he never tries it again after his adventure in Narnia. In the Voyage of the Dawn Treader, I was disappointed with Lewis for putting a wizard/magician in it at the castle with the funny little people who have one large foot. Lucy is the only one who can cast the spell to make them visible, because she is a pure-hearted little girl. Now Lewis used a wizard, in his story, and he was a good wizard and there was a spell book and a spell was cast. I don't think I can judge him because I have written similar stories. I've never had anything published however, just written for fun, I've written fan fiction and put it on sites on the internet for friends to read.
In the silver chair there's and evil sorceress again, and again she is defeated by good. I've also read the Last battle, where there is something of and end to Narnia, but not quite, more like Judgment Day for the Narnians. I love the Chronicles of Narnia!