I have done testing from the link below of all the games.
Any games that took too long to load (over 15 seconds) or were way too choppy were not deemed usable. So check out the list below to save yourself hours of time testing like I did.
I assume that with newer firmware updates it's possible that the Archos may play these games better, but really there is only so much a 500-600Mhz CPU can do. So for now enjoy! My favorites are Harry the Hampster, Twins, Irritating Game, Hexxagon and Pipes.
Also, does anyone have any idea as to what sort of graphics chip the Archos 605/705 have, or at least a guess as to how much video ram it has?