id go with shang hai, as it is the next location for the worlds fair. it depends what youre into though. ive always wanted to see the teracata warriors in xian who were buried thousands of years ago. another good one is the silk road. the road that many westerners traveled to get to
china back in the day, including marco polo. hainan is a good place if you like the beach, and tropical type atmosphere. its a huge country like canada, but each city is really different.
china has 52 different ethnic groups. all very different. i know alot of local chinese find xinjiang to be very interesting because it is a turkish type region with mostly muslims. tibet is also a tourist destination for locals and foreigners. if youre looking for modern, then go to shang hai. as paris hilton has said, it looks like the future.