I think Waikiki is the prettiest beach in Hawaii, without a doubt and I have been to Maui, HNL, and Kauai. Hawaii traditionally isn't a beach destination per se. All the hotel beaches have public access, that is just the way it is from when it was being developed. I love Kauai, it is the prettiest island. The big island is interesting and has wonderful public beaches but it's my least favorite, but it is still wonderful. It has such a diverse topography. Desert, rain forest, volcano's etc. But the Hyatt in Kauai is a wonderful spot for family and couples.