Cars Land is great, but Potter is based on a series that is essentially written as if the author were designing a theme park. There is in-depth description of visually uncanny environments, exotic food and beverage, retail experiences, magical vehicles, etc. On top of that, because the novels came first, a far greater proportion of people interested in Harry Potter will have read the extended accompanying literary material; I imagine a comparison between the number of Potter fans who have read the various books and the number of Star Wars fans who have read the novelizations/extended universe info will favor the former. Within the context of, say, the few Avatar or Star Wars films, the treatment of any one setting is pretty much surface-level only, so to fill in F&B, retail, etc., you have to either invent things or dig into supplementary materials with which most visitors won't be familiar. That's not to say that there aren't a few iconic things that you can place in the "other" lands that will draw people in (e.g. Millennium Falcon for Star Wars, floating islands for Pandora, Peach's Castle for Mario, etc.), but there are not many properties that hit so fully and completely on the entire nexus of things that make a theme park tick. Everyone who's coming in already wants to shop at Ollivander's and Gambol & Japes, already wants to try butterbeer and chocolate frogs, already wants to explore the depths of Gringotts and the Escher-like halls of Hogwarts, already wants to ride the train, already wants to dine at the Leaky Cauldron. You don't have to invent things like Satu'li or Toad's Cafe and subsequently convince people of the interest, desirability, and value. You just have to deliver the quality; the familiarity is already there unlike with almost anything else you could build.
