Two old school classics.
Duck hunt is a 2D shooting game using Nintendo's lightgun. Basicly you can shoot clay discs or 1-2 ducks per round. The ducks get progressively faster and you have to 'down' or shoot so many ducks per level to advance. The number of ducks that you can miss lowers as you progress to higher levels.
Super Mario Brothers is a 2D scroller where you jump, run, and advance thru the levels to save the princess and defeat King Koopa. Its hard to expain, and its sad if you haven't played this game yet!!!