Gears of War cannot be compared to other AAA PS3 and 360 titles because Epic used their own Unreal Engine 3. Any other developer has to either build their own engine (effing expensive) or license another strong engine (still pretty effing expensive).
The numbers I have heard (and as others have pointed out, there are a great many acceptions) for high-end games are:
Wii: 5-10 Million
360: 15-20 Million
PS3: 20-25 Million (with truly humongous, graphics-hungry games costing upwards of 30 Million....looking at you K2)
starcraft - Playing Games = FUN, Talking about Games = SERIOUS







