The "black" women posted to show how "beautiful" they are...
look white.
Light eyes, high cheekbones, sharp features... those are Caucasian traits.
The more AFRICAN or negroid a woman looks, the uglier. Some of the eastern ones -- David Bowie's wife comes to mind -- have lots of white blood.
I think there's a good measure of objectivity here -- as opposed to the subjectivity of a man of X race preferring women of X race. Whites just have universally appealing looks. You have to strain for "good looking" black men (Blair Underwood? Denzel Washington?), Hispanic and Asian men, too. They're rare. The white women are the best. They're ironically more "diverse" in appearance than women of other races: red hair, black hair, blonde hair, brown hair. Blue eyes, green eyes, gray eyes, brown eyes (chicks with light brown eyes can be SO HOT). Black, Hispanic and Asian women are just... um, black brown and yellow. Hair, always black. Yippee. Every white man has a little thing for Asian women, but genetically, Asians are the closest race to whites, so it makes sense.