Sorry for the delay.
Went to Oahu and Maui did the road to Hanna (yawn, the drive on the other side of the island the car rental companies tell you not to go to was much more impressive), the plane ride over is horrendous, the islands (at least where we went) while surely beautiful have nothing on say most anything in the Caribbean most especially the American and British Virgin Islands which are about a 1000x easier to get to.
Fully acknowledge, however, there are likely some great ones I missed of course (and admittedly one called the blue pool was nice as it was right on the ocean) on the other islands, but with what we did see I stand by my statement:
the biggest waterfalls in Hawaii google image search
The biggest waterfalls in Ithaca ny Google image search
(Edit for some reason the links won't paste!)