If you are dead set on playing an Assassin's Creed game inside a PS2 emulator (PCSX2) for nostalgia's sake:
The search for "assassins creed ps2 iso" is a perfect case study in digital preservation psychology. assassins creed ps2iso
If you own a PS3 (any model), you can buy the original Assassin's Creed PS3 disc. All PS3 models play PS3 games. Some early PS3 models also play PS2 games, but again, there is no PS2 disc to insert. If you are dead set on playing an
Towards the end of the PS2's life, Ubisoft released compilation discs that technically put Assassin's Creed on the system. These are often confused with the main ISO: assassins creed ps2iso