I like dating black girls, because they are the only way white guys like me can get into clubs!!!
But seriously, the majority of my girlfriends were black (I only had one white girlfriend my whole life). But for me, I don't think it has ever been a matter of preference, but rather from when I was one year old until I was 10, all my friends and neighbours were black, even my first church was a predominantly black church. I didn't actually have white friends or acquaintances until my teen years (and even then, the amount of white friends in my life was extremely limited). So I assume because of that, I have always felt much more comfortable and natural around black women than white women.
To be completely honest (and I'm not joking here) when I eventually did date a white girl (which was not until in my early thirties), it was actually quite weird for me to be with a white girl. Even my black and Indian friends said it was weird for them to see me with a white girl - lol.
So I guess my point is, everyone is different, and even when attraction to other races is present, the attraction does not always have to be based on the physical per say, but sometimes upbringing can be a factor as well (for me, it was familiarity with black women that made me attracted to them, not the fact that they were not white).
Twice I reversed the question, and I did ask two of my black girlfriends "Why do black women like me so much?" and they actually both had the same reaction - they simply laughed out loud. To this day I don't know what their laughter meant, but at least I can still get into clubs - lol.