Half Life 2 is not the best game of the decade. Neither is World of Warcraft.
World of Warcraft is fun, and they're updating it frequently to make it more, or less fun. Half Life 2 is one story line, is a relatively generic FPS with a great storyline.
The only reason most of you are voting for HL2 is because most of you are obsessed with TF2, and even without playing the game, you think it's an amazing game because Valve made it.
World of Warcraft doesn't deserve the game of the decade, either. It gets boring fast, though it's got some replay value, considering it's got a variety of things to do. Though, unless you make a friend or two in-game, or bring a couple of friends from real life, it will get repetitive and you'll want to stop playing once you hit level 20.
Frankly, I think I've had more fun playing Oblivion, Dragon Age: Origins or Left 4 Dead more than I've had playing either of these.
