A technical comparison of today's top game engines
To give you an idea of how weird it is to see people comparing a Valve engine to an id engine, consider that without id, Valve probably wouldn't be in existence. Gabe Newell left Microsoft and went into game development after he talked to the id development team and saw what they were doing. Even more ironic is that Half-Life used the Quake licensed engine from id. Now these are the top engines out there and something no other game will be able to top for a couple of years (Unreal Engine 3). Here's a comparison of each engine, not game, in each critical area of game development.
News source: DevMaster.net