Square Enix's role-playing game Final Fantasy XIII is a PlayStation 3. (And an Xbox 360 game!) But at one time, the game was running on the PS2.
Early artwork and screens have been published in two new books from Square Enix, giving insight into the game's design process. These test version images date pre-E3 2006 when the game was announced, and thus, are logically running on the PS2.
The art direction is different than what appeared in the final product. The battle user interface doesn't look that different, however.