Someone has managed to create a version of Super Mario Bros. (NES) for the Atari 2600. The ROM and source are available here:
www.atariage.com/forums/topic/201426-sup...d-1-1-playable-demo/

I think it's a pretty decent attempt at a platformer, given the 2600's limitations.

That's got surprisingly accurate controls for a one button game.

That... is pretty good o.o
Didn't know the Atari had such a competent sound chip