I think in Asia, most people want to emulate caucasians. That's why everyone wants to have white milky skin and that's why brands like Anna Sui have a whitening cream range that is only available in Asia and not abroad. Same with L'oreal. Basically, there is a general consensus in Asia that Asian girls are not as pretty as their caucasian counterparts which is why you may hear people say "So so is pretty....... for an Asian". Based on this, to criticize an Asian actress in comparison to caucasian actresses means that even a pretty Asian actress would be deemed hideous.
That's why I think people tend to compare Asians to their own race. Another thing is, with most Asian actresses who make it "big" in Hollywood like Gong Li, Bai Ling, Michelle Yeo, Zhang Ziyi, they develop this horrible attitude where they think they're really hot sh*t because they're Asian and from China or wherever and still made it big. You have to remember Hollywood may seem like a big deal in America/Europe but it's an even bigger deal in Asia. A lot of people look up to caucasians in HK. So many local girls here want to go out with expat boyfriends. I'm not really sure why either but my cousin is local here and she absolutely dotes on Caucasian males. For some reason, she thinks ALL caucasian males are attractive even though some are really quite hideous. I think it's a cultural thing. I don't think Lucy Liu is like that though. Maybe cause she grew up in America. But I read an interview with Katie Leung somewhere and she already sounded a bit stuck up. I know she grew up in Scotland.. but still.
Anyway the point is, causians and asians have different standards of beauty and like I said, it's probably a cultural thing which may be sad, but it's the truth!