While originally an exclusive for the Sony PlayStation 3, there are several modern methods to experience the game: God of War III - Playstation 3 - Amazon.com
Download the official RPCS3 emulator from rpcs3.net . Install the PS3 firmware from Sony’s official website (this is legal).
Set the CPU to "LLVM Recompiler." Set the GPU to "Vulkan." Enable "Write Color Buffers" and "Read Color Buffers." Disable "VSync."
If you own the original PS3 Blu-ray disc of God of War III , you can legally create your own ISO for backup/emulation purposes. However, this requires:
A: You either have a bad dump, or you forgot to decrypt the ISO. PS3 discs are encrypted; you cannot just copy the files. You must use a decryption tool with a disc key.