Just remember everyone's experience and expectations are different. It's really what you are looking for in vacation. Cancun is very commercialized and very "American". By that I mean big resorts with familiar names, shopping and restaurants you would see in any American city. But it's comfortable, affordable and accessible for most Americans and that's why it's popular.
Head south along the Rivera Maya and you find less commercial development and more destination resorts where relaxation, surf and Spa's are popular, this area is also very popular with the Europeans.
Playa Del Carmen is a charming smaller town, great restaurants and shopping, more laid back than Cancun, and it's the gateway to Cozumel with great snorkeling and diving. Further south on your way to Tulum you start finding more condominium and hotel developments popular with American and Canadian snowbirds. Past Tulum you really start getting into the wild parts of Mexico, lots of "adventure" style accommodations, hiking, biking are popular, much more earthy, popular with the younger crowd.
Another area to consider is Isla Mujeres off the coast of Cancun, just starting to get developed, and Merida on the other side of the Yucatan peninsula, a colonial city, lots of culture, not on the ocean though.
I own a travel agency specializing in Mexico, if you have any questions please don't hesitate to ask.