I would say a good female character has to be able to carry the weight of the role on her shoulders well. Especially if she is the main character. It has to be believable that she is capable of not just holding her own in a fight (if need be), but also capable of being more than a girl who can kick your ass. She has to be more than one dimensional, she has to be smart and have a vulnerable side. Being pretty is not a bad thing, but there's more to a pretty face than you see.
Lara Croft from the 2013 Tomb Raider game is a good example.