You must provide a PS2 BIOS file to start the emulator. You can legally dump this from your own PS2 console.
This treatise explains running the original God of War (PS2) on PC using the PCSX2 emulator, covering requirements, setup, configuration, performance tips, legal considerations, and troubleshooting. It assumes you already own a legitimate copy of the game and a PS2 BIOS dump from your own console.
Even with perfect settings, you might encounter hiccups. Here’s how to fix them.