Two of the best games for the NES!
Super Mario Bros. is also crazy addictive. What you have to do in this game is save the princess form Bowser. You will have to defeat your enemies by jumping on them or throwing fireballs at them. There are some strange power-ups such as a mushroom that makes Mario become Super Mario, a flower that gives Mario the ability to shoot fireballs, and the star which temporarily makes Mario invincible. There are a total of 8 worlds, each with 4 levels in them.
Both of these games are classics and they helped put Nintendo on the map! I highly recommend both of these games to anyone.