We've been to most of the Grand Mayan properties, but we love the Riviera Maya one best! You fly into Cancun airport and grab a rental car for the most flexibility. Then you can explore the whole coast from Cancun down to the Belize border. Starting with Cirque du Soleil ON SITE for a spectacular show in addition to many water-related features and shows available.
On down the coast there's interesting small towns like Playa del Carmen and Puerto Morales to explore. And a short ferry ride from Playa Del Carmen there's the Island of Cozumel. Further down the coast is Tulum with its culturally significant artifacts. The opportunities abound!