Millipede (1984) (Atari) ROM

 
I first played this game when I was 6 years old.  I thought it was very hard, and I still do.  This is one of the few games that pose a true challenge to any player of any age or skill level.  That merit alone should make this game a shoe in for “classic” status.  The gameplay and simple premise of the game are everlasting and will never go out of style. 
The goal of the game is to rack up as many points as possible before (inevitably) you lose all of your lives and get a game over.  The story is simple enough:  You play as a garden gnome fending off a millipede attack by firing shots at the segments one by one.  When you succeed in defeating a centipede, another, faster one spawns and you must defeat it before it arrives at your location.  If it does, you have to dodge its remaining scurrying segments whilst firing at the various threats from all directions.  If you are hit by any object, it takes one life.  The obstacles are stationary mushrooms, poison earwigs, resilient bees, dodgy spiders, annoying beetles, helpful inchworms, evasive dragonflies, beneficial mosquitos, effective DDT bombs, and indestructible flowers.  All while an increasingly fast millipede continues to charge you.  All of this difficulty and variety makes for an intense and fun experience every time. 
It only gets stale after a long time of enjoyment, and a sharp realization that you’ll never beat the world record.  Since there’s no such thing as ever beating the game, you will put it down eventually, but it’s fun while it lasts.