Not necessarily true, its preference, but majority of guys like straight hair. It just looks nice, neat, clean, and sometimes sexy. I find curly hair more attractive myself, my closest lady friend has the most amazing natural curly hair and almost everyone tells her its gorgeous. I know its hard to deal with a majority, but quanity or quality, what are you looking for?
Honestly I think it's more about being able to pull off the hair style. A lot of people say straight hair because it's one of the simplest styles and most girls can pull it off, however not everyone looks good with curly hair! If it's your natural texture then I'd say stick with it :) I personally have wavy hair and even though I straighten it from time to time I LOVE curly hair and always wished I had natural curls so you should own your curls proudly! :)