I have seen/visited but not stayed at several of the Marriott properties on the different islands, and they are all fine, but, in my opinion, not great, exciting, exotic, etc. There is one exception which I'd recommend highly (and I have stayed there): it's the JW Marriott Ihiliani on the tip of Oahu. Architectually, it is as arresting as the setting is beautiful: I believe it was originally built by the Japanese before it became a Marriott property, which accounts for it not looking like all the other Marriotts in Hawaii. It is a 30-45 minute drive from the airport, but it is away from the conjestion around Diamondhead, and still within easy driving distance if you want to go to the Royal Hawaiian for a drink or explore Pearl Harbor.
If being in the center of the action is your main focus, I would not recommend this hotel. But otherwise, the atmosphere and the setting and the architecture combine to make you feel like you are really in Hawaii, and not just another beach resort which could be anywhere.
I agree the hotel and surrounding area are beaurtiful. We stayed at the MVC Koalina timeshare a few years ago, which is a short walk from the JW. The restaurants in the hotel were excellent at that time. This was a relaxing alternative to the noise and congestion on Wakiki.