You've named the heavy hitters: Assassin's Creed, Mafia II, Prototype, GTA IV/V, inFAMOUS, Just Cause 2, RDR, The Saboteur, BioShock (linear), Borderlands (looter-shooter), Saints Row, Yakuza 3. Here are **overlooked or distinct** PS3 sandboxes worth playing:
Start with **Sleeping Dogs** and **LittleBigPlanet 2**—they're the most polished "different" experiences.