It comes down to Tokyo or California, really. The other resorts all have yet to fill out their existing parks (that is, the ~$4-5 billion it would take to build a compelling fifth gate at WDW would be used much more efficiently by expanding the four that already exist). Even then, DCA should get a phase 2, and an expansion to Tokyo Disneyland park wouldn't hurt.
I go with Tokyo only because they've committed to spending on enhancing the existing parks as it is. If you want a third gate, you can't let your old parks get stale, otherwise you just get cannibalization.