The scales look rather varied, but I suppose with a bit of greebling you could make some passable ships. The McDonalds toys of a few years ago (both the small ones and the larger ones with heads on top) had much better detailing. The Kinder gunship seems really plain.
I've got a batch of the McD's clone gunships that I keep meaning to paint up for 10mm.
I've got a couple on release out of curiosity (and not knowing what type the toys were). The Millenium Falcon actually is none too shabby (I got two) and would just need some puttying up to be usable as a game piece. For 6mm, though, the things are rather small, IMHO (they are "box scale", pretty much, though, as eilif says), as all the ships are only 1.5inches across, tops. The Falcon would be around 1/1200 scale, I'd estimate.