Hands down, very useful and interesting thread. I would like to add my 2 cents here, based on my experience and observation
I am an European (Caucasian) guy, who did his undergrad in West Europe and also did a study abroad semester in the US. What I noticed is:
*Guys generally, very few exceptions, don`t really care about the race of the girl. What is the most important thing is looks. Guys like attractive girls and diversity makes it even better
* Caucasian girls have strong preference towards North American and European guys. Rarely had I seen white (and attractive girl ) with a black guy. Never had I seen white girl with an asian guy.
* Looks play an extremely important part (especially in Europe). I cannot really say which gender tends to be more selective in terms of looks, but this tendency was more evident in Europe. Perhaps because ,generally speaking, people in Europe tend to care more about their appearance and , on average, both males and females look attractive, wearing the latest clothes, parfumes and so on..
* People in Europe tend to be much more conservative and prejudiced. A guy I met in Belgium told me that his grandather had told him he would leave him without inheritance unless he brings home a white (preferably blond) wife. I think in this regard people in Europe are at the level at which the ones in the US were in the 1970s.
* This is based strictly on one conversation with a Japanese girl. She told me that when dating, girls tend to think very long term and she would not, personally, date a guy from a country, in which she cannot envision herself living.