In terms of sexual selection, East Asian women have the most gracile features. This doesn't mean they are 'the most attractive,' since that phrasing is inevitably a matter of personal opinion. However we can modify the question a bit so it has an objective answer:

All other things equal, what race of woman would the highest number of men find to be most attractive, on average?

For purposes of simplicity we will ignore the conditioning that people go through to be attracted to this or that (not something that can be ignored IRL, but you understand). East Asian women are more neotenous, more gracile, slighter of frame, less inclined towards corpulence, and more demure by nature. However, East Asians have the lowest genetic diversity of all races, and are most genetically distinct from the original African type. Remember, as you move away from Africa, genetic diversity decreases. Therefore they are 'more different' from other races than other races are to each other, and there are fewer outliers, generally speaking. So while as a matter of evolution, East Asian women are probably the most universally attractive on average, we ought not to expect them to have as many standouts as other races. So they would be more beautiful on average, but rarely would an East Asian be the most beautiful individual example. Most people probably don't think about this in terms of averages and instead visualize a handful of the most attractive women they have ever seen, probably settling on 'white' unless they have a particular inclination. But that is hardly a scientific way to answer the question. Think of all the homely women in that mental sample that you have left out. There are probably more unfortunate looking white women than East Asians (per capita), if you're really honest.

It's a shame that the African females are generally considered unattractive. It isn't their fault. They only had to compete with each other in Africa, where the dark complexion and more robust features, higher testosterone, etc., were all useful in that environment. Now they have to compete with hyper-gracile Asian females and white standouts that just weren't around in their ancestral environment. However for that same reason, black men are considered more attractive in the West (and East Asian men less so). According to this notion, though, some of the most beautiful individual women in the world would be at least partially black, rare as they might be. Take that as you will.

At the level of physical attraction, it's all reducible to simple universals as matters of ontogeny and endocrinological development. We're still apes at the end of the day. The psychological element makes things much more complex--I could write a whole thesis about that, which is why I did write a whole thesis about that, back in my masters days.