[seventhtiger]

If Animal Crossing and The Sims are games, then so is a doll house or a bit of play dough.

I subscribe to Chris Crawford's definition. Games are competitions between multiple players and they must be able to interfere with each other. A painting, a toy, a puzzle, a race, are all not games. The difference between taking a stroll while carrying a ball and playing a game is keeping score.

The most controversial result of that is that God of War and Dark Souls are actually puzzles, and not games, and although it's unintuitive upon reflection it rings true to me.