try comparing SMAP, GACKT or morning musume to the project imas crew. who is more busy?
Why compare an idol/singing group to a game group
as a whole? Obviously the latter has more time, as it takes months to a few years, at the most, to make a game. And when one half of the team finished their job, then they are no longer busy, but that doesn't remove the fact that the stress brought by doing their work is practically the same. And in before the counter, I'm pretty sure both the former and the latter has a schedule to fulfill the requirements of their jobs.
If counting only CVs, it is, as you said before editing your message, "all dependent on popularity." Also, For the case of iM@S, let's be honest and say that not much people know or took regard to the voice actors. They, and the rest of any game group, make that up for live performances, no?