well, setting aside personal prefs on talent, what you're talking about is money.
if a lot of people go to see SOUL PLANE, then lots of versions of SOUL PLANE will be made. If no one goes to see A SOLDIER'S STORY, it will be blamed on the mostly black cast and the themes of the story.
This kind of ties into some of the other stuff we were talking about on the Tyler Perry/Spike thread.
One of the good things that can be said about Perry is that he gives folks work.
Dude puts out a movie ever other year with machine-like regularity.
Back in the glory days of the 90's (shakes heads sadly) you had Spike's joints, a buppie rom-com and whatever 'hood film came out that year.
Stuff now has slowed down somewhat to where Perry seems to be the only guy hitting the screen on the regular(its kind of an odd thing too-hood films still make money. But they come out far less then they used to.)
This state of affairs probably affects Rashida Jones far less than say, Theresa Randle. Jones has the dough and connections to get a production company up and running to create roles for her.