icloud not saving game data

I have an ipad and iphone 4s but icloud never saves the game data. EG: GTA 3 is compatibale with ipad, ipod touch and iphone. So should it synch the saved game data to each idevice as the same app is compatibale with all the idevices.

But some apps like talking tom 2 are not comptibale with each other so you have to buy it seperate for ipad and iphone.

I really want to synch saved game data apps with each on my ipad and iphone, because sometimes I may be out and want to play the game or app on my iphone.

Thanks