The Atari 7800 ProSystem
The graphics chip GCC developed was called Maria, and could push almost 100 sprites on the screen without any of the annoying flicker the 2600 had become known for. Another impressive feature of the 7800 is it's backward compatibility with the mega popular 2600. This gave it an instant library of games and alleviated one of the major complaints 5200 owners had. (BTW, the 7800 was the first console to feature backward compatibility long before Gameboy Advance and PlayStation 2.) The 7800 was also to have a cartridge for saving high scores and a keyboard attachment. Neither of which was released by Atari, but the high score cart was released by Curt Vendel in 2003. Curt is also working on releasing the keyboard attachment.
As for the joystick, the 7800 ProLine fixed many of the problems known with the 5200 sticks. ProLines were self-centering, had fewer buttons, but retained the elongated handle. Due to that fact, the ProLine controllers rank right behind the 5200 sticks as the worst controllers from Atari. (Atari would later offer a joypad similar to those from Nintendo and Sega.)
So, Atari was all set to release the 7800 when the bottom fell out of the video game industry around 1984. Once Jack Tramiel and his family took over, the 7800 was shelved and placed in a warehouse. "We're a computer company now!" Tramiel is said to have screamed in a meeting.
Then something truly special happened... Nintendo revived the video game industry by introducing the Nintendo Entertainment System (NES) as a toy. Tramiel and company felt they should do something with the aging 7800 units and began selling them and creating some new games for the system. So, in a way, we have Nintendo to thank for giving us the 7800.