I've only seen the two US castles in person -don't really have the desire to see the others but might some day. If I'm in Paris, Tokyo, Shanghai ...there's many more things to do than going to a Disney Park for my time(although I love them).
I believe it's Cinderella Castle because they didn't want the castles to be possessive -so it's more of a title. As in, the Washington Memorial -not Washington's Memorial.