The oldest system I have is an Atari 2600 and, although it doesn't get the same play time as the others, I do plug it in very often to play Enduro, Keystone Capers, and lots of Freeway against the wife (she's really good). I'm also planning to give River Raid some serious attention sometime. I love the game, but suck at it.

That, and it's the only console allowed to sit beside the television on the TV Rack of Mild Destruction - the other ones rest is the space right below the set. My wife says it looks "vintage", way cooler then the others, and therefore deserves to be a part of the living room decoration...