The PS2 version of Call of Duty: World at War (developed by Treyarch/Rebellion) is a significantly scaled-down port distinct from the "next-gen" versions. Here are the key differences:
The PS2 version is a "demake"—a distinct product built on older tech. It offers the core WWII shooter fantasy but lacks the spectacle, co-op, Zombies, and deep multiplayer that defined the game on PS3/360/PC. For the definitive experience, play on a modern platform or via backward compatibility.