In general, games on the 7800 and 800 are the ones to go for over the 2600. One exception in my opinion is Mrs. Pacman. I perfer that on the 2600 due to its superior playability over the 7800. But most other games I would say, such as Joust or donkey kong are better on the 7800 and 800xl. Between the 800xl and 7800 I am unsure.
You can check out game lists for all 3 systems at my Atari Web site at www.netcolony.com/members/addie
RE: 2600 vs. 7800 vs. 800 XL 