Seeing this thread makes me happy indeed! It'd be silly for me to offer my own such list, as like Phonedave, I've really only experienced WDW. Well, I've also experienced Gatorland, which comes very, very close. But it's great to see everyon else's reflections on the matter.
Also, it's great to see the Haunted Mansion recognized by everyone! It makes me happy to realize that the version I finally got to revisit is the greatest in the world.
As a bit of an afterthought, I'd like to humbly submit one notion for inclusion on the list - the awesome legacy of the Orange Bird. Did TDL ever have an Orange Bird? Well, DID IT???