The scene releases don't actually use iso's. Just the file structure of the game.
Average multiplatform game is around 6gb. Final Fantasy XIII is 40gb, God of War III is 40gb, Heavy Rain is 17gb, Resistance 2 is 18gb. There aren't a ton of games dumped yet.
Oh, to the people who keep saying that Sony copied the Wii.
Not true, Sony has had a patent for what is now known as Move since 2004. Long before the Wii was announced.