Excluding EPCOT, weren't the Marriott parks the last of the fully planned and built themed parks from the original "theme park" boom of the 60's and 70's? After that I think it was acquisition and conversion of existing traditional, animal and water parks into full fledged theme parks.
I think that the Marriott's GREAT AMERICA parks were pretty much the last of the major theme parks built on "green fields" of that era. Many years later, parks like Legoland California, Disney's California Adventure, and Universal Studios Islands of Adventure were also built new.
That's what I thought. I remember shortly after the Marriott parks opened I read an article about how there were going to be no new theme parks built because the market was saturated (no major metropolitan areas left to support them). Things sure have changed since then.