You may have to use a different person, but I swear to God the one that worked for me repeatedly in the early 90's was "Wow, has anyone ever told you that you look exactly like Madonna?" In context, it was kind of funny because I'd be saying it to some girl that really had no physical characteristics similar to Madonna whatsoever - even girls of different ethnicities who could not, in any manner, be considered to be a Madonna clone.

Of course, then there's the line that I always talked about using and never did (I think Rodney Dangerfield used something similar in Back to School):

Me: "Wow, that dress really looks nice on you"
She: "Oh? Thanks."
Me: "I bet it'll look even better crumpled up on my bedroom floor tomorrow morning".