Spore

Take a look at one of the future games being put out by Maxis, makers of The Sims.

http://www.spore.com/about.php

Basically, it's similar in concept to The Sims, but you evolve from the cellular origins of life all the way to the point where you are colonizing other planets. It's pretty ambitious and I could see this being way more addicting than The Sims, based on the countless ways that your creatures could turn out (You earn DNA points along the way which allows you to "buy" certain characteristics, allowing you to survive).

Check out the official trailer which can be found here.

Any wagers on how long before right wing organizations start sending out press releases condemning this game as being sent by the devil? I wonder if they'll be allowed to play this in Kansas...