What do you consider "nicest?" Each one has it's benefits which vary based on where you are traveling. For example....Starwood is best IMHO for Italy and Greece since they have the most hotels in those areas.

Are you asking specifically for Hong Kong?

I would suggest that you look at the various card options offered by Starwood, Hilton, Marriott, Intercontinental and Hyatt. Then compare the earnings potential and sign up bonuses and also the availability of hotels in the areas you are looking to travel and then chose a card accordingly.