I have given many women some of the most lovely compliments that I could think of, and gotten many positive reactions.
However, when I got to know some exceptionally beautiful women, I asked them if they got a lot of compliments...
Surprisingly they said it was very RARE. They said most guys just stare, and "gawk." And some guys act scared of them. I told them that a lot of guys out there are intimidated by beauty (needless to say...THAT was a compliment in itself). Most said something like, "Thank you! I needed that."
DON'T be afraid to tell a beautiful woman that she IS beautiful.
Just because she is a total knockout does not mean that she does not need a sincere compliment. Perhaps she does. I was sure surprised to find out that these women I talked to RARELY get complimented on their beauty, so I was more than happy to oblige.