Liora,
I read a few other comments that have been posted since my first post and pretty much everyone is echoing the same idea. Its unfortunate that you heard this your whole life, and are therefore attributing a great amount of importance to it. Although, I do give you credit for sharing this openly with your chosson, that shows that you can discuss issues which bother you (even if they may sound silly to others) and that’s very important in a marriage. Food for thought: Don’t you know any sefardim married to ashkenazim? Tall people married to short people? etc. I think if you would rack your brain enough you could think of several examples of wonderful marriages where the two parties do not look alike. And if you really can’t think of anyone, then just realize that chances are that the issues these couples face, or that any couple faces for that matter, has very little to do with their physical appearances being different, and more likely has to do with differences in personality/outlook on life/goals in life/hashkafa etc.