Spore: Skinning the game
Skinners, gamers, and users Unite!!
http://www.spore.com/screenshots.php?movieID=9&play=hiSoon we may have a game that brings us all together and evens the playing field. That game is Spore by EA and Maxis
Fight with other creatures and consume them to adjust the form and abilities of your creature. It's survival of the fittest at the most microscopic level.
Creature Phase
Venture
onto land and help your creature learn and evolve with forays away from
your nest. The only way to grow is by taking chances!
Tribal Phase
Instead
of controlling an individual creature, you are now caring for an entire
tribe. Give them tools and guide their interactions as you upgrade
their state of existence.
Civilization Phase
Once
your city is established, your creatures begin seeking out and
interacting with other cultures. Make contact with an olive branch or a
war cry. The goal for your creatures is to conquer the planet.
Space Phase
The time has come to move on to other worlds in your solar system. Make contact, colonize, or terraform, then venture further to find other solar systems. A 'mission' structure provides new goals in your quest for galactic dominance.

One of the most interesting aspects is that even though this is a single player game, other players creatures at or near the same evolutionary stage as your creature will be downloaded for your creature to interact with. Very cool
You can find out a bit more on the FAQ