girls "seem" to cry more because it is more acceptable for them to cry. if a dude cries, well oh well he's weak or a sissy and so on. the pressure to be masculine is placed on guy by society. to appear weak is not acceptable. what people don't realize is that crying, by anyone, is a good form of emotional release.
excessive crying is not a good thing though. it is often a sign of an emotional problem. then again some people just cry just like that.