BEIJING -- Legendary explorer Marco Polo's journey to China lasted 24 years. This is the kind of commitment that foreign media executives leading the way into China today say they will have to show their hosts if they are to succeed at making a business out of entertaining 1.3 billion Chinese. They continue their push into China with new partnerships and ventures taking shape on a regular basis, but the majors realize that it might be 20 or even 30 years before they can reap the full benefits of these exploratory ventures. Executives who are leading the way into China...