Game of the Year

Many mega blockbuster games are taking on the shelves this holiday season. If I had to choose one among all these great games...Half Life 2 by Valve is the winner. I don't think the game is perfect, but I like the direction the developers of this game have taken. Their source engine has helped simulate a world more closely resembling our reality:

Characters - Advanced facial animation system delivers the most sophisticated in-game characters ever seen. With 40 distinct facial "muscles," human characters convey the full array of human emotion, and respond to the player with fluidity and intelligence.

Physics - From pebbles to water to 2-ton trucks respond as expected, as they obey the laws of mass, friction, gravity, and buoyancy.

Graphics - Source’s shader-based renderer, like the one used at Pixar to create movies such as Toy Story® and Monster's, Inc.®, creates the most beautiful and realistic environments ever seen in a video game.

AI - Neither friends nor enemies charge blindly into the fray. They can assess threats, navigate tricky terrain, and fashion weapons from whatever is at hand.

I'd like to add that level design is also worth noting. It keeps the adrenaline rushing and the game is fast paced consistently. Other things include all those little things like shooting the birds and breaking/throwing random objects throughout the world.
The minimum specs of this game, however, are pretty high. And I do advise playing it on a cutting edge PC. I wouldn't waste the time otherwise.

Note: My pick was among games like Halo 2, Metal Gear Solid 3, World of Warcraft, GTA: San Andreas, NFS Underground 2, Sims 2, etc... I do still need to check out Prince of Persia: Warrior Within and Gran Turismo 4 before the year end.