What the Atari 2600 was pushed to achieved years later is pretty impressive when you consider it was only designed to play
Pong (and variants therof).
Rom size has a lot to do with some of the more impressive efforts. During the height of the 2600 most games were probably 4k, rom space was extremely expensive.. atari was cheap.. and there's only so much you can cram into 4k. Look at a late 80s game with 16k or 32k rom and its night and day.
http://www.youtube.com/watch?v=3wo8-6GPnBQ2600 Rampage was pretty impressive for what it was.. but then again by the time this came out you had to really be the 'poor kid' if you were buying 2600 games.
I did pick up 2600
Ghostbusters simply because I was so damned curious about how they managed to shove a relatively complicated games into the 2600. They actually did an amazing job all things considered but its not replacing the 8-bit computer versions.
With games like Double Dragon its impressive that the 2600 can play
anything that resembles Double Dragon once again given how far from
Pong or
Breakout the concept is. But once again at time it came out very few people would have been excited about finally getting that port to their Atari.