First of all, a fetish is a very particular and narrow liking of a part of type of object, act, or concept, such as the liking lighter skinned people not because they are people but because of how the lightness of the skin reacts with the specular of light reflection (Green 2002).

In most Asian cultures, there is an admiration of lighter skin. If you notice that most cosmetic products in Asian contain some form of skin lightening. I know this from personal experience as part of my family comes from an Asian culture. I have extremely light skin, and a lot of my relatives have pointed out their envy of that.

But to say what the motivations are, whether it is a fetish or some more complex interest in the profile of a person with lighter skin, we have to go into the minds of everyone with that interest and it's difficult to draw that conclusion.

I can say that I believe it is more of a fetish, as most Asians that I know come from a closed-culture and even after the Open Door policy was established, many Asians are weary of "white people" and do not believe in "inter-species mating". So chances are, it is probably more common for that to be a fetish in my opinion.

As for non-Asians having a fetish for Asians, we do know that most western people (men in particular) prefer the emaciated girl that looks like a little boy with unrealistically large (some times artificial) breasts, as evident in western movies, TV, and advertising.

Asians, in reality, come in all shapes and sizes, in fact, Asians are on average TALLER than Caucasians. However because Asian figures tend to have an inverse bell curve in terms of height and build (either really short and skinny, or really tall and well built), there is the possibility to say that there exists a fetish for Asians in that the particularness is that Asian females (and males) look like little emaciated boys, and its easily surgically altered with breast implants to satisfy the desire for overly large breasts.