I'm Japanese and my boyfriend is white. I think he is absolutely gorgeous. His soft blonde hair, the blue eyes; always give me butterflies. But it's funny that I never thought so before I got to know him. I was kind of limiting myself to Asians back then. But once I realized his intelligence, wittiness and care, I knew he was special. Day by day he became more and more physically attractive to me.
So I think it all comes down to how emotionally you are attracted to someone. Because honestly, I find all races attractive. As long as you love who he or she is, any relationship, whether it'd be interracial or not, will work. Oh and the culture thing. Aside from loving his or her character, if your two cultures are compatible (way of thinking, acting, beliefs), or if you two are willing to make sacrifices culturally for each other, you'll have a great relationship.
What I'm trying to say is, neither is better than the other. If the person you happened to fall in love with turned out to be a different ethnicity than you, that's awesome. But don't limit yourself to just non-mexican girls.