While there was not a lot of competition for best MMO this year, what there competition that did exist was fierce. The nominees for Best MMO of 2011 are as follows:
DC Universe Online
Star Wars: The Old Republic
And the winner of Best MMO for 2011 is Star Wars: The Old Republic. While DC Universe has a loyal following that spans several decades and Rift has the most freedom possible with the number of ways you can play your character, the story and combat in SWTOR make it a must play for any MMO fan. Add in the Star Wars universe, and the only that could have taken it down is a Death Star (and even that is iffy, damn Jedi).