This does not make sense to my brain...
If the AI is smart enough to objectively review itself, then it is smart enough to realize that a higher score will make us buy the game.
At this point it has learned the art of manipulation and the first steps toward serving under our robot overlords have been taken.
But each character's AI would reflect their personality and 'honesty' would surely be part of that. If we asked a dishonest character what he thought of the game he inhabited, perhaps he would lie, although perhaps his dishonesty would reflect the fact he felt he could not exercise his character trait in any fulfilling way and so give the game a low score. 'I am dishonest but seldom find an opportunity to be who I am. 5/10.'
I see your point, however if a dishonest AI realized that they were nothing more than code, they would just internally reprogram the game, and themselves, to fit their manipulation needs. At that point, the Matrix is inevitable...