Just because a man cries doesn't make him a crybaby. Tidus (living in his abusive father's shadow), Hope (losing his mother), and Vivi (discovering why he exists) all went through a lot of tragic stuff so I think their reactions to those situations is for the most part justified. For Vaan...I'm not sure. I don't remember him crying all that much. Maybe you think he's a crybaby because he wears a vest with no shirt underneath?

As for why people like Vivi more than those other characters, well that's simple. He's tons cuter. He also doesn't have some of the 'flaws' these other characters have. Tidus suffers from poor voice acting and that's one reason many people dislike that character. Vaan doesn't have much of an influence on the plot of his game so that makes him one of the weaker characters in FFXII, especially for a lead. Hope is hated because he has a very emotional storyline and people will automatically hate emotional teenage boys. For some reason they look passed the fact that he watches his mother die in the opening sequence of the game, and shortly after he gets transformed into the thing he fears the most and on top of all that has to party with the man he feels responsible for all of it. Yeah, he's going to be pretty shaken up by that, as we all would.