I would recommend you review the resort reviews here on TUG to get a good overview as well as specific feedback on the various resorts. This is a personal view and will vary based on one's experiences and preferences. However, based on our experiences to date, I would list the following as our favorite five resorts:
1. Maui Ocean Club- Napili and Lahaina Towers (ocean front or ocean view): rooms are extremely nice and the location is outstanding.
2. Ko Olina (ocean view): once again, beautiful resort with very nice rooms. A remote location on Oahu, but have access to all of things to do on the island.
3. Desert Springs Villas 1: our favorite desert resort. Very nice grounds and large units (maybe the largest in the system). Partial access to JW Marriott next door.
4. Newport Coast: large resort on the Southern CA coast. Access to a beach (walking), Los Angeles and San Diego for day trips, nice weather
5. Frenchman's Cove, St Thomas- good Carribean location, beach, day trips to St John.
It is hard for us after the first four as there are so many resorts that we've stayed at and really like. That is part of the beauty of the Marriott program. With that in mind, others that we have enjoyed are: Grand Ocean in Hilton Head, Ocean Point in West Palm Beach, Cypress Harbour in Orlando, Ocean Club in Aruba, and Desert Ridge in Phoenix. If you want night life,etc. Grand Chateau in Las Vegas is in a great location one block off the strip.
We will be visiting the resort in Marbella this fall and have heard great things about that one too.
Visit them all I say! Happy vacationing.
Mike