My MMO of the Decade, (and the other 4 top games of the Decade)
Is Everquest. Not Wow, not EQ2 (though I believe, correct me if I'm wrong, it introduced some really important mechanics).
Because it got things started. The argument for WoW is basically, "WoW is hugely popular, 100 times more popular than any other MMO. And that means it has reached the conciousness of popular culture."
These are big accomplishments. But Everquest really put together the package and got the ball rolling. Most of the architecture of all MMO's are based on that of Everquest, with variations.
Wow has certainly changed the industry, as company after company tries to be "the next WoW". But they have all failed. So which is more influential?
Ten years from now I might decide that I was wrong and should have picked EVE Online. But I think that's an long shot. EVE is successful because it it contrarian, I think.
Ok, the other four games of the decade are:
Texas Hold'em. This game was televised regularly during the Oughts. And featured in a James Bond movie, replacing the baccarat game of the original Casino Royale.
Guitar Hero This game came before Rock Band, which I think has surpassed GH. But it gets the nod for showing us a whole new way of interacting with a video console, and opening up entire new markets. Near misses are Wii Sports and Wii Fit.
Carcassonne Board gaming is back and much more interesting than it was in the days of Monopoly and Chutes and Ladders. Settlers of Catan may have led this charge in the 90's, but the 00's belonged to Carcassonne. Right now the hot game is Dominion, but it's too early to tell how influential it will be.
Dungeons and Dragons The last decade has seen 3rd Edition, released in 2000, 3.5, released in 2003, and 4th edition. WOTC also rewrote the rules on how supplements and modules are released with the Open Gaming License. And with very few exceptions, all MMORPG's and lots of console RPG's use D&D's basic model: characters with stats that kill things, level up, get new gear, get new abilities. D&D had a great year.
This is my personal list. What's yours?
UPDATE: I hit publish yesterday by accident, and the resulting post showed an inability to count to 5. It's fixed now.