Aside from white people being the dominant group in the west and the medias influence on what is attractive, it's largely a personal thing depending on your background and experiences with people and your personal psychology.
I'm black and as far as men are concerned, I definitely prefer white guys. I'm not really into black guys but this isn't a common preference among black women at all. I'm bisexual and I don't really have a preference there. I guess if I had to pick a group of women I am least attracted to, it would be Asian women. Having said that, I am attracted to many Asian women. The next person may disagree with me. In fact I'm sure a lot of people find Asian women to be gorgeous and the best in terms of looks.
Also regardless of my preferences, it doesn't mean I literally think white people are the most attractive objectively. There's a difference. I can recognize lots of attractive people, in my opinion, and not be personally attracted to them in a sexual or romantic context. That's not the same thing as thinking white people are better looking than everyone else on average because I definitely don't agree with that.
I also think race blankets things a lot. Not all groups of "white people" look the same or share the same common features. Someone may not really be attracted to blond, pale men but love the olive skinned, Mediterranean men. Just like not all Asians look the same or black people or "Latinos" (not a race), etc. and there's the individual factor and the fact that there are tons of unattractive white people, imo. Like, a lot of them. In certain environments, I feel like I'm better looking than 99% of the white people in the room. Other situations, not so much. So when people say things things its often considering only part of the equation, unless you just think paper skin looks better, or something along those lines, then you will probably favor one group above everyone else. And I mean aside from preferences, but I guess it's true in that sense too. I don't think white guys are better looking in general but I'm definitely more attracted to them in terms of sex or relationships. But I'm also attracted to guys of other races, just not many black guys. I don't think black men are the least attractive objectively, aside from my preferences though. I can see beauty in all kinds of people and a lot of black men are very attractive. But I'm not usually attracted TO them...
Tell me if I'm making any kind of sense lol