I read Harry Potter. I play the cardgame Magic: The Gathering. I like Final Fantasy. I have explanations for each one though.
In Harry Potter, it does get kind of dark, but I know that it's jsut a story and that the book reinforces the characters doing good things, not bad things.
Magic: The Gathering is just a cardgame. Some people think that it's deep into occultic stuff, but I beg to differ. (On a website against M:tG, they claimed that to play a card, you have hold up your hand and say "Spirits enter me." Complete fiction. Like the cardgame itself. ^_^ Where are people making this stuff up from?) You aren't really forced deep into the fantasy setting or anything. It just gives the game depth and flavor. When you play a spell, you don't have to pretend to summon spirits or say an incantation to do it. You just turn a few cards sideways to indicate you're paying for it, then you announce which card you're playing and lay it down on the table. Occultic? I think not. However, some cards are very creepy or occultic in flavor, but they don't encourage it in any way. The type of card that does that the most are black cards, and black always ends up damaging itself in meeting its ends. Black cards often invlolve using your own life points to get effects, but it ends up killing itself in the end. That's why I play Green cards, which are very different in nature and play style from black cards. You play in a completely different way if you sue a different color of cards, so it's not like every single card in the game is occultic or something.
Final Fantasy isn't flooded with Magic or naything. the most you see in it is a character their hands together and mumbling, followed by a fireball or a healing spell or something. Or maybe the summoner makes a creepy critter appear and fry the baddies. Again, it's nothing like real world occult practices.
In the end, if you know that it's fantasy, and you don't let it make you slip closer to the real stuff, there's no problem with it. And remember, if you feel yourself slipping, spend some time praying/reading the Bible and you'll feel as if four inch titanium spikes have grown out of your shoes. Try slipping while wearing those.