Let's get one thing out of the way: I have never read a single Harry Potter novel. Not because I dislike them or have a passionate anti-Christian fervor or whatever it is that gets people to dislike them (all my vitriol is saved for Twilight), but because I don't care much for fantasy novels. They're not my thing. Sci-fi isn't, either. That's not to say I've never read a fantasy book and wound up being entertained. For example, I did enjoy Ender's Game by Orson Scott Card. I recognize good writing and good prose and good storytelling when I see it and that is universal, regardless of the genre.
I read fifty or so pages of the first book, Sorcerer's Stone, a while back. It didn't wow me or impress me and I more or less let it go. That said, it is easy to see why readers gravitated to the novels. J.K. Rowling does a very good job of playing to the universal themes of someone discovering their destiny, learning who they are as a person, and everything that was more or less present in Star Wars. Like the aforementioned, Rowling brings an element of the supernatural and has a vivid fervor in her to write the stories, which is something you can't deny.
The books and movies have been enormously successful because of the continuing quality of both products. Will they last the test of time? Maybe. Certainly our lifetimes. After that? Hard to say. Like anything else in history, only the rare few survive to be remembered.
After more than a decade, it is all over. It seems strange, but there it is. There's been talk of Rowling writing an eighth book. I say that is a colossal mistake. As I understand it, she said everything she needed to say. Only reason she would write an eighth is for money. Fans might want it now, but then you have to listen to them bitch. Remember the prequel trilogy for Star Wars and the fourth Indiana Jones movie?
Let Harry rest. For the millions and millions of fans out there, it was one hell of a ride.