Tetris is a game that doesn't even need any explanation, might be the one game everybody in the world has already seen it. What some people might not know is the size of the game, how big it was, and the fact that you could play in basically any system you could have at the time, and still can, even today.
For most people it was the number one game to play in a Gameboy. It's one of the classics that will never guy, by it's simplicity.