Both the writers and Jennifer Morrison have confirmed that Emma is a new fairytale character they created, so it is safe to say that Henry is, too. 😀 That said, they also admitted that they did base story of The Ugly Duckling on Emma–how she goes through many changes and all. And I can see comparing Emma to Alice–
1). Both enter into a strange world that they are not used to.
2). Both are surrounded my oddities (Storybrooke is not a normal town) and don’t really have any idea on how to approach them.
3). Both are very curious.
4). Both affect the world they are in.
5). And the story does closely follow them. I know there are other main character in Once Upon A Time, but Emma is one of them that are closely followed.
Henry is very much like his family–he is brave, courageous, strong, curious, and smart. He certainly has a Prince-like edge to him for some reason. the way he dresses and holds himself, as well as what he says.
I have a feeling that he is the center simply for how he brought everyone together. He is the reason Emma decided to stay in Storybrooke. And because she stayed, time moved forward.