Personally, I did not like Wikiki on Oahu. Last year I went on a cruise around a handful of the islands - Maui and the Big Island stick out in my mind. Maui has a lot to do with many different places to stay - after the cruise my bf and I stayed for 5 days in Maui. We rented a condo off Craigslist for a very good price. I also liked the Big Island, I really liked Kona in particular. It all depends on what you want to do - you should get a Hawaii Frodors travel book.
Good luck!!