I am LOVING Ghost Trick: Phantom Detective (DS) at the moment. Some FANTASTIC 2D characterisations and a REALLY interesting story. The basic premise is that you're dead, you don't know how or why you died, but you have the power to possess different objects and raise the recently dead by reversing time by four minutes before they were killed, watching events play out and then changing them. It's the story that pulls it through though, there are some unique characters and a really good story that keeps you playing through the chapters.
The ONLY thing is there is one solution to each puzzle and thus as much as the concept seems quite fluid, it's very LINEAR. But still rewarding.