When you see a download for a "GTA 4 PS2 ISO," it typically refers to one of three things:

Technical limitations prevented Rockstar from porting the game to older hardware:

: In some regions, unofficial "pirated" discs were sold with GTA 4 cover art, but the disc inside usually contained a modded San Andreas or another game entirely. Why a Real GTA 4 Port for PS2 was Impossible