this seems like a REALLY easy thing to fix.
step 1) do not allow retailers to sell games that have a rating higher than the age of the buyer. (its supposed to be like this already, but it still happens.)
step 2) if a parent is buying the game for the kid, TELL THEM ABOUT THE RATING! make sure they understand that they are buying a game with blood and violence and strong language or whatever, for their 8 yr old.
step 3) optionally, in the case of a kid getting someone who is not their parent to buy the game for them, get a signature and a phone number or something..