Sony is undoubtedly leading the way in experimental games, by developing several out of the box titles, that are downloadable from the PS3 Network store.  The tops are:

Flow
In, Flow the user manipulates the sixaxis controller to navigate a simple single celled organism in a rich 3D aquatic environment.  Watch your organism evolve based on what it eats.  Are you aggressive? Watch your creature evolve bigger pinchers to catch prey.  Will you cannibalize your own kind?  Can you defend yourself against predators?

The story behind Flow is pretty interesting as well.  Seems that the original idea was an MFA Thesis, that some minds at Sony were smart enough to co-opt. Check out the online version of the game, to get a sense of how it plays on the PS3 console.  Check out the trailer below:

 

Just when you thought Sony reached the apex of experimental games, along comes EchoChrome.  Imagine being able to spin around and manipulate M.C. Escher’s creations, as a means of solving complex visual puzzles, and you have EchoChrome.  Check out an example here:

 

And lastly, check out the irresistible guilty pleasure of the new PS3 native WIPEOUT HD.  The Wachowski Brothers seem to have taken some cues from the WIPEOUT franchise for their latest creation, Speed Racer.