Can't say I've ever played a game that my family was ever into, but I know the feeling of doing something good in a game and even though I'm not exactly rewarded for it, just knowing I did something good always felt like it's own reward.
I've always hated when games give you the standard "You saved a family so you get good points, but because you killed all those police officers before you get evil points". I think a game can be extremely strong with simply letting the world react to your actions as opposed to displaying a physical appearance change or other moral displays as such. Games like Fable and Mass Effect are very interesting to me (despite the need to change your appearance because you did X and Y) because the world tends to change depending on your actions.
Dishonored is already exploring these methods with it's Chaos system which is something I'm DYING to hear more about. Either way it's a good warm fuzzy feeling knowing I've done something good in a game even if it doesn't change the story what so ever.