Again, after a Question is raised anybody is bound to think about it.
As far as I've observed, out of hundreds of tweets many seemed to have voted for Harry Potter.
But then, I might have missed observing many tweets.
It's like when you want to buy clothes, all of a sudden you'll find cloth stores everywhere. Otherwise while walking on that street everyday you might not have observed those shops ever, they even exist.
Well then why do I like Harry Potter?
Harry Potter is a story of some supernatural power. Yet he is not a sole super hero. He's just one among every other in his society. He's a simple boy like most others. Yet he is famous.
We tend to relate with him instantly. Then he goes to school, he studies, he writes exams, he gets punished. He lives in a Hostel with fellow students. He travels by train. He's just like us, we can relate to him.
Harry Potter's world is just similar to that of ours. There is a school, there are teachers, there are friends, there are rivals at school, there are sports, there are competitions. There's a Ministry, which works all most like our Governments. There's media, which also works like our media. That makes the life in Harry Potter familier.
Perhaps this made most of Harry Potter fans love Harry Potter.
Narnia is a pure fantasy, a beautiful story. We watch it and enjoy it.
Harry Potter is like Gulliver Travels, a complete satire on our present society. Harry Potter touches our lives. It's a great epic of modern literature.
I conclude, you can't compare two different things, while Harry Potter is liked for:
a) Ms J.K.Rowling's brilliance and
b) Warner Brothers' efforts in making that world real for us and
c) not to forget making Harry Potter and his friends grow in front of our eyes.