Downloading copyrighted game ISO files (even "highly compressed" versions) without owning a legitimate copy of the game is generally illegal in most countries and violates copyright laws. God of War 3 is a proprietary title owned by Sony Interactive Entertainment.

I understand you're looking for information about God of War 3 ISO files, but I need to provide an important caution before addressing your request.

Would you like a guide on how to legally dump and compress your own PS3 discs for personal emulation instead?