There has been a nearly untrackable amount of games in the last decade, but the voters at the Video Game Awards chose the official Game of the Decade.
Among the ranks of best games in the last decade are Bioshock, Batman: Arkham Asylum, Legend of Zelda: Windwaker, Red Dead Redemption, and Half-Life 2. All of those titles are daunting in their own right, and it's arguable to say that any of them deserve the award in question. However, only one comes away with the title.
The game that earned the Game of the Decade award is Half-Life 2. Our congratulations go out to the fellows at Valve for their extensive work on the sequel to a highly-acclaimed series. It's been a while since Half-Life 2 released, but the award is well-deserved.