Five years ago Quantic Dream struck a nerve with Indigo Prophecy (Fahrenheit). The game was not a financial success but it received moderate critical acclaim for it's innovations in story telling and cinematic gameplay. Quantic Dream's upcoming PS3 title Heavy Rain is a game that is hard to categorize to a specific genre.  I'd almost go so far as to say that Heavy Rain is an interactive movie. It's a game I definitily recommend trying before buying.

A playable demo is available in the PSN store.