My vote is for the game "Clue".
It's a simple game that young children can learn and enjoy. When they first start playing, they use simple elimination. As they progress they can continue to more advanced strategies. They learn to observe what the other players are asking of each other, who's passing and on what guesses.
Clue may not be a game that adults will play on their own, but when it comes to including the little ones, it's fantastic.