When I was actively going after Atari 2600 lots I was always getting doubles, triples, quadruples, etc of the dirt common games. I've gotten rid of almost all the doubles but at one time I had plastic bin upon plastic bin full of combats, pacmans, space invaders, asteroids, etc. Its just the nature of collecting. These are the games that EVERYONE owned if they had a 2600. Just like SMB/DH for the NES or Sonic for the Genesis.
Even rarer consoles have their common games like Keith Courage for the TG-16. I'm a big Tandy color computer collector and there hasn't been one lot I've bought that didn't have a copy of megabug with it.