It really depends on the girl. I find that most women look best in their natural hair be it straight, curly or wavy.
That being said, I have noticed a pattern in my sexual behavior: I tend to fall for women with very curly hair. Something like Shakira's hair when natural, and even very thick curly hair seems to get me. I also like medium length in general and have a soft spot for either very short or very long hair.
Unlike most men, I find certain short cuts very feminine and attractive.