Number 7: Onyxia and the 5th anniversary
Can you believe that this game is still going this strong after five years old? In mid-August, Blizzard released patch 3.2.2, which re-introduced Onyxia, the game's first raid, as a special anniversary encounter. And then on November 23rd, this game, which still commands more of an audience than even most brand new games do, turned five years old. Blizzard told us all sorts of stories about how they did it, from the early trepidation (soothed by one of their bosses saying that they'd have "a million subscribers" someday), to the first launch night and the subsequent scrambling for more and more servers to keep players in the game. And all throughout the anniversary, even while other MMOs are closing up shop already, having started and finished their development all inside WoW's uptime, no one doubts this game won't go on for five years more at least.
Number 6: Patch 3.1
This is the first of the three major content patches this year -- it dropped in April as the first content patch of Wrath of the Lich King, and brought us both Ulduar and the beginnings of the Argent Tournament. The tournament turned out to be (once we built it) a huge competition that introduced not only a new jousting mechanic to the game, but some new ways to gain old reputation, and lots of various rewards to earn. Class changes came thick in this patch as well -- the death knight nerfs made news, major priest and warlock spells were redesigned, and hunters made news for what they didn't get: their expected ammo changes (which still aren't in the game at the end of 2009). But Ulduar made this one worth it -- all of its various fights, achievements, and hard modes are still keeping players busy on raid night.
Number 5: BlizzCon 2009
I was liveblogging the opening ceremonies of BlizzCon 2009 when they played that Cataclysm trailer for the first time, and at the very end, when Deathwing appeared, they actually lit real pyro on the stage. A theater full of thousands of people all jumped in their seats, including me. BlizzCon 2009 brought that earthquake to the whole community this year -- when we finally saw what Blizzard officially had planned in all of their panels and interviews (Path of the Titans! A whole world redone!), had our gigantic meetup (complete with The Guild making cameos), and at the end of it all, had Ozzy rock the entire building, we were all jumping out of our seats with excitement. BlizzCon and all of its worgen and goblins and Ghostcrawler and Kerrigans and Diablos shook up the entire world of Blizzard this year.