Originally Posted by
Pickles
Let me give you the counter-argument. I don't (willingly) eat sushi outside of Japan. Can you find good sushi outside of Japan? Yes, but (a) it's hard to find, (b) inconsistent, and (c) much more expensive than the equivalent quality in Japan. So why bother setting myself up for disappointment at some highly-rated place in, say, New York, paying through the nose, for something that, at best, equals what you can find in Japan?
...And, would I go out of my way to seek it as a visitor to Japan? Absolutely not.
This is all true, but fails to account for obvious reasons why one might want to eat Chinese food, Sushi, or other foods in foreign countries. Often, one does not have the ability at any given moment to travel the world to eat a particular type of food. Even if one resides in or frequently travels to Hong Kong or Tokyo, one might want to eat Chinese food or sushi with a particular person who does not. One might also want to eat a favorite food while abroad for an extended period of time.
While the best Sushi in the world can only be found in Tokyo, in cities like New York fish and other ingredients can be flown in easily enough if they cannot be sourced more locally. The result as you say is usually sushi that is at best adequate by Tokyo standards, and of course the price is much higher. Nevertheless, for those who cannot easily make it to Tokyo, or for Japanese expatriates living in New York, this is still appealing.
Chinese food is a bit less specialized than sushi (the type of sushi discussed here is specific to Tokyo), and the ingredients are much easier to obtain in foreign countries, especially in Japan or other parts of Asia. In Japan, I would contend that Chinese food can be produced with greater success than good sushi can be in New York. The best Chinese food in Japan is obviously not as good as the best Chinese food in China, but is still probably better than >90% of Chinese food in China. Of course the cost of high-end Chinese food in Japan is very high, but again for many people it can be appealing.
As you appear to have HK as one of your locations, and obviously spend a lot of time in Japan, it is understandable that eating the local foods where you are would make more sense. Others might not travel to China frequently or at all, which may be the case for the OP. For an American traveling to Japan who has no immediate plans to travel to China, it could absolutely make sense to have a Chinese meal in Tokyo, as it's still pretty damn good and in any event far better than what is available in the US.