Super Mario Bros. Classic
Platformers are all about movement: running, jumping and timing your way across levels full of gaps, enemies and secrets. The best ones feel great to control within seconds and then slowly teach you to master every leap.
Typical commitment: an evening or two. Tip: Retro platformers often have limited lives and few checkpoints. Learn one level at a time, look for hidden 1-ups, and don't be shy about using a save feature when it is available.