This is a commentary on Harry Potter books I and II. My first HP essay, so be kind!
One reason the Harry Potter books are so popular is that JK Rowling uses themes that appeal to most kids, and to many adults who enjoy the fantasy genre. One of them is the "unwanted/unappreciated child" theme. This has at least two variants. The unwanted child achieves a greater destiny than their unappreciative family gave them credit for, or the unwanted child discovers their true identity and it's greater than their unappreciative family knew or was willing to own up to.
These are themes found in Cinderella and The Ugly Duckling, respectively.
In the Dursley family, Harry is of course Cinderella, the unwanted, "ugly" family relation who gets treated like crap. In "Philosopher's Stone", Harry crawls out of his cupboard (just Cinderella has her place at the hearth) and has to make the Dursleys their breakfast like a slave while the spoiled Dudley is lavished with gifts and can only complain about not getting as many as last year. This family situation is so over-the-top it's deliberately meant to be fairy-tale-like.
And just like in the fairy tale, one day the fairy godparent (Hagrid) comes along and guides the unwanted/unappreciated child (Harry) to his greater destiny, and he leaves his unappreciative truly ugly family behind with their noses in the dust.
In the Dursley family, Harry Potter is also the Ugly Duckling: a child misplaced among people who are not his own kind. They see him as ugly and inferior, when in fact he belongs to an entirely different "species", and among his own kind, he is considered beautiful and superior. His kind are in awe of him.
This is powerful stuff to people who have always felt out of place and picked on. I always related to the Ugly Duckling story. Someday I would be among people who would appreciate me! Not you sorry ugly lot who are kicking me around the school yard for not being pretty enough.
But see, in the Ugly Duckling story, once the bird finds out he's actually a beautiful swan, the story ends. We all assume he lives happily ever after. In Cinderella, once Cinderella marries the prince, the story ends. And we're supposed to believe she lives "happily ever after".
But the story of Harry Potter only really truly begins when Harry steps into his birth-righted world. Then things get iffy.
On the one hand, you have the "Harry Potter celebrity worship" Harry receives as he steps into the Wizard's world. Show'm your scar and get invited to all the best parties. And you have Dumbledore, McGonagall and Hagrid doting on Harry and letting him get away with breaking more than one school rule in hopes that he will rise up in the ranks of heroism and Quidditch. One also gets the impression they feel like his adoptive parents. So he goes from being an outsider among Muggles to the ultimate insider in the Wizard world.
And he lives up to his new family's expecations more than once, but not before getting in trouble both for things he did and things he didn't do.
So on the other hand, you have many people in the Magic world hating Harry for NOT living up to their expectations of "Harry Potter". He's not elitist enough for Malfoy. Snape and Filch seem to hate him and bait him just because he's a "celebrity".
All this just makes Harry more popular with Rowling's readers, because he is the humble celebrity. In The Chamber of Secrets, Gilderoy Lockhart is brought into the story as Harry's opposite to make this evident: Lockhart is the boasting, self-congratulatory celebrity who has actually accomplished nothing; Harry is the quiet, self-deprecating celebrity who has beaten the evil Voldemort twice and manages to do it again by the end of the book.
Likewise, Harry befriends the ordinary folk of the Magic world: the non-elite Weasleys and the mudbloods. Is it any wonder that the 95% percent of the world that is unappreciated and average and longing to be recognized for greatness eat up Rowling's books with a spoon?
But Harry's existence is a very mixed bag. It is a long way from "happily ever after". He makes mistakes. He is constantly challenged to prove himself. And he is a morally complex individual who will be forced to struggle many times with the temptations and miseries of celebrity, power, and adolescence.
I'm going to end this here and leave it open for any discussion. I may not respond to all of it, since I haven't read books 3-5 yet and I don't want to be spoiled.