I've dated mostly Mexicans, one white guy, and El Salvadoran guy. For me he was really exotic looking. Very dark skin, curly frizzy hair, his Spanish was different from what I hear. I'm Mexican-American. He almost looked black. To me he was really different. Although El Salvador and Mexico is the same thing, being latin. But it's different cultures. He had different custom and beliefs than Mexicans.
I'm not sure what would quantify someone as being 'most exotic' for a white girl? hah but my ex was Fijian, current boyfriend is Chinese. My current one wasn't born here and the family functions of his that I go to are not very white-washed or Americanized at all. Any adjustments in cuisine and all are made because they know I'll be there. :P