The data are in and Hong Kong is victorious: based on 2012 travel patterns (apparently these studies take some time to compile) the HKSAR drew more visitors than any other city in the world. That that, Singapore (3rd) and Bangkok (4th place).
Now, not to rain on Hong Kong's parade, but the fact that visitors from mainland China counted as "international travelers" does pretty significantly skew the results. The Wall Street Journal blog covered HK's new ranking and they admitted, "to be sure, a large portion of the visits from the mainland to Hong Kong are day-trippers from neighboring Shenzhen looking to stock up on daily necessities, such as milk powder."
When New York City (ranked 8th) gets "international travelers," they come from, well, other countries. With Hong Kong, it's a bit sketchier.
This is just fair warning for when Euromonitor (the company who ran this study) publishes its "Top 100 City Destinations" as some kind of hot travel guide, readers should be wary that many of their fellow "international" travelers will be a bunch of Guangdongers running to snag some milk powder, update their Facebook apps, orgive people avian flu.