
The Atari 8-bit line (400/800/XL/XE) had a lot of games, and I'd call it the second best gaming machine of the 80s, after the NES. It had RPGs, adventure games, action games, and most of the same ports that the 5200 did. I liked the XL/XE version of Donkey Kong better than Nintendo's NES version, in part because that was one of the few versions to have all four levels in it. Most home versions omitted the Cement Factory level, including the NES version.
And the best part was that you could play all these great games with a standard 2600 joystick instead of the horrible 5200 joystick. So the 8-bit line was basically what a really great version of the 5200 would have been like. And later on, I found out that Genesis controllers would work perfectly on the Atari 8-bit, since they both have the same 9-pin connectors.
Anyway, those were suggestions if you wanted to stretch this out to a twelve-part series.