The Atari 2600 is for people who enjoy old school games, and do not care if its not 10 GBs big and just 1 MB. The Atari is a simplier gaming system, it may not be 3D, have incredible sounds, or have massive game play, but its an old school classic.
If you really like a game, it will always be fun to play it again. Atari games are still great even after all this time. Look at all the collections of classic games released again for PlayStation 2. Some games never get old.
Atari 2600 classics are STILL easily played for hours on end in my collection. The problem with Atari though is that there were HUNDREDS and HUNDREDS of games pumped out. Anyone could sit down and program a game and put it out, and at the height of the gaming rush dozens of subpar games were being released for every good game.
Not everyone is as impressed with Huge 3D worlds and graphics as they are with the playability of a game. For fans of true strategy games and puzzle games, there's nothing better than the classics...
My mom had one of these that I found and I plugged it in and played it for a little over two days but the games just could not keep me happy. There was one that was fun it was Called Burger-Time. That was the only one that I played for more then an hour.