Why do people like the Harry Potter and Twilight series so much?

I've read all the Harry Potter books, but I've never read Twilight before. Harry Potter was pretty decent but I just don't see what's so great about it. I mean Harry got pretty annoying when he became fourteen or so and I don't know it just doesn't seem all that great compared to other fantasy books that I've read like The Book of Lost Things, The Chronicles of Narnia, Graveyard Book, American Gods, The Name of The Wind etc. Not trying to be offensive or anything. Maybe it's because I'm only eleven and both of those series seem to be intended for adolescents(not saying that grown ups can't like them).