I agree. The thing about idea generation is you have your influences that give you the initial spark. You make something different by combining parts of these influences together and adding your own creativity. You also get inspiration from real life.
The two story lines may be similar but the magic for both of them is the little things that make the world it is set in so special. They are unique to themselves. It is the sub plots and the little details.
It has been a long time since I saw star wars (I may re watch them). So I can't give an example there. All I can say is it had a completely different feel to Harry Potter.
What makes Harry Potter so special for me is how it was a completely magical world (everything was thought of from the sweets to houses, laws), yet it still felt so familiar like it was everyday life.