I think the biggest thing where people go wrong when comparing Harry Potter to Narnia, and Lord of the Rings, is this; Harry Potter was written by a non-christian, the idea was secular, whether its about "Good", or "Bad". Harry Potter is about witchcraft, and although I've never read the books, I have seen a few of the movies from other people watching them. They contain a few swears, bits of sexual references, and pure nonsense. Narnia, and Lord of the Rings on the other hand, are referenced to the Bible, both with Christian writers behind the stories. Though they may contain "magic" its the evil people doing it, not the good (Despite Gandalf). So you see the difference? Harry Potter, everyone is using magic doesn't matter if your "Good", or "Bad" its all secular. Narnia/Lord of the Rings, Only the evil use it (Minus Gandalf). Lord of the Rings/Narnia shows you that magic is evil. Harry Potter gives you the go ahead to do it, its okay whether your "Good", or "Bad".
Isaiah 41:13 "For I am the LORD your God who takes hold of your right hand and says to you, Do not fear; I will help you."
Hebrews 13:5 "Keep your lives free from the love of money and be content with what you have, because God has said,
'Never will I leave you;
never will I forsake you.'"
Jesus will not leave you, even when everyone else deserts you, he never will.