If you're talking about fun gameplay, I might say Katamari Damacy. Plus it's just smurfing adorable. Also, Baldur's Gate. For the...PS2. xD I've played that game so many times. I don't know what it is about it, it's really not all that great. Maybe it's the nostalgia. Dunno. Whatever it is.
I also love Silent Hill's gameplay. All of thems.