...on my Atari 2600 I've got this Tennis game Activision did which is so simple, it's Brillant. The game itself I think is only 2k in size. It only gives you one set, and the graphics are simple (as most 2600 games are), though the playability of it is perfect and the difficulty of the Computer player is also spot on - it has two difficulty levels I think, and you can also play against a human player.
It maybe simple in many regards, though in this case, I think making it simple has allow them to produce something which is fun to play.