Well, i think everything is on physics, voice and animations. I will love a game that reacts like a real life girl, i mean, where you put the bullet, the character feels the wound. For example, if she gets a crotch shot or arrow in the groin, she go down inmediately, grabbing her groin in agony until she dies or you execute her. (Saints row 3, GoldenEye 64 are the closer games that i can think they do that). Also, they will need a lot of different reactions and voices. One girl could beg for her life, another can try to crawl for escape, etc. Physics are important too, i wish a game with not a premade animations of impact, every bullet, punch, kick or object must react different depending of character's angle, if she is running, jumping, crouching, etc. (A wonderful example is Overwgrowth) Finally, i think the body and clothes should react realistic too. I mean, today only boobs giggle "realistic" in games, but i think the entire body must look soft and react to enviroment. Also the clothes, must be fully removable and dynamic. The kind of game could be anyone, i am talking about the "game engine"