Spore

The game spore is an simply awesome game! You get to do all sorts of fun stuff in Spore, including making your own creature, making your own virtual civilization, battling against other creatures, sharing your creature online and etc. There are multiple stages in the game, including civilization mode, - this is where you can create cities and have wars with other creatures' cities - space mode - you explore space in a spaceship and go on missions to, for example, search for life on another planet. All I can say is that it's quite a "groovy" game!
Spore is available for both PC and Mac, and the creature creator is available for DS and the IPhone/IPod Touch. Happy Gaming!