What is the difference between Harry Potter and CS Lewis Narnia? Why is CS not bad?

More churches are ok with CS Lewis' writing than with J.K. Rowling's because CS Lewis was a Christian whose books had underlying Christian themes. However I feel that the reasoning behind why the Church thinks HP is bad is not really reasonable (They say HP will turn people into Satan worshipers). If you have faith that you and your children are able to enjoy a fiction movie without finding the overwhelming urge to worship the Devil then you can watch Harry Potter.