Matt:
Response #2 (not much different than #1 but prompted by some other posts.
Oahu:
1) Oahu CC
2) Kaneohe Clipper (north shore through the Pali Tunnel)
3) Royal Kunia
4) Mid-Pac
Kauai:
Poipu Bay, Grove Farms, Kauai Lagoon and, lastly, The Prince. As JohnV said, too many lay-ups off the tee.
Big Island:
Mauna Kea has the long-standing rep because it was (allegedly) the first "really good" course in Hawai'i that was part of the first real luxury resort that had been built in the state since the 1920's. Although Oahu CC has always been good, it's private and it is true that the 2 best holes at MK are really, really good (#3 plus some par 3 on the back - #11? I think).
Other than that, the course and, to a lesser degree, the hotel have definitely been surpassed by at least 6 courses on the Big Island alone - all of which have been mentioned here, already.
Lanai:
Challenge at Manele is definitely worth a boat trip over from Maui for the day. Fabulous vistas, 4 or 5 spectacular holes - kind of like Pebble Beach in Hawai'i. The Greg Norman course at Koehle (spell?) Lodge (up the mountain) is only worth it if you're staying there.