Running this on Android via is impressive because the PSP (PlayStation Portable) had a less powerful processor than the PS2. However, Sony ported God of War II to the PSP with incredible optimization. The PSP version is slightly downscaled (lower resolution textures, fewer on-screen enemies), which makes it perfect for mobile emulation.
Legitimate versions of the God of War PSP games are often compressed into (Compressed ISO) formats to save space: god of war 2 iso highly compressed for android ppsspp
However, if you cannot find a physical copy, and you are using a compressed ISO purely because you already own the game and want to play it on your phone, you are in the emulation "grey area." Use your judgment. Running this on Android via is impressive because