they won't ever be tbh. Each one now is under 20 bucks, new if you can find it that way. considering their worth and their personal worth to me, I'd never part with them.
supreme commander was promising on the 360, but the 360 couldnt handle the game what so ever. It completely breaks the game when you start pushing about 60 units and it becomes unplayable. The PC version is pretty amazing though. Im hoping the second one that is coming out on the 360 is actually playable. No unit limit, extremely large maps, etc