I will agree that for the most part LA has SF beat on Asian food, but Cantonese/HK style Chinese is better in SF, and the rest is probably on par, just fewer options in SF.

But you nailed in on the head -- you have to find ethnic food made by people who know how it's supposed to taste and making it for people who know how it's supposed to taste. If I go into an ethnic restaurant I know it's good if the majority of the customers are that ethnicity.