I see a lot of haters here, frankly unjustified.
1. There have been trailers for wow patches for like 5 years now, this is not new. Welcome to the internet.
2. I can pretty much guarrantee that if you took Warcraft 3 Arthas at max level (with Frostmourne and all) and put him up against 25 non-hero knights, he would lose.
3. 12 million people playing this game doesn't say anything about whether this game is good or bad. It only proves this game is popular. Any of your comments about the player quantity, however, also do not prove if the game is good or bad. For that, you need to log in, play the game (preferably more than just run around naked), and then come here and write in your completely subjective terms what you liked or didn't like about the game. Until then, your argument is zero.
4. In my completely subjective opinion, the trailer is mediocre. They could have done a lot better than your standard "prepare to fight boss - fight boss - kill boss - rejoice" plotline, and they could have done a lot better than "hey look it's a massive army at my gates, all my teritory in Northrend has been lost, my castle is under attack, the spirits in my blade are likely going to wake up and backstab me, 90% of my undead army is now no longer undead, my allies have been thoroughly defeated and humiliated every day, my enemies have been organizing championships of who gets to kill me which i thoroughly failed to stop, BUT WHO CARES ABOUT THE DETAILS I CAN STILL KILL THEM. DURR.". You have to wonder if reducing Arthas to stardard-game-villain#54536 dumbs down the plot's credibility and complexity a bit.
And in my opinion based on 3 years of experience, WoW is a lot better MMO than any other out there. It's still an MMO though.