One of the challenges with the 7800 is it felt like Atari first dusted off the old GCC titles. Then they cheaply tried to port computer titles, while focusing on the XEGS. By the time they started working on NES like games (ala Plutos, Sirius, Commando, Alien Brigade, Scrapyard Dog, Midnight Mutants, Basketbrawl, Klax, Toki etc), the system was losing shelf space to the 16-bit systems and many people never saw the games that were released, let alone the ones that got mothballed. To this day, there are people that think it's nothing more than an advanced Centipede playing machine.
Rikki and Vikki and Bentley Bear's Crystal Quest are two nice gems made by homebrewers.