This year (2009)!
Plenty of things happened in my life, so will 2010!
If I also have to say my worst year, it would be 2008. Too much of precipitations (rain/snow), and boredom centric year, filled with disappointements, particulary on video games.
2009 has to be my favorite though. Great year. Got my first girlfriend, a new PC, a few new friends, a bomb threat at my school, and a couple of snow days. Also a good year for game releases.
I think I'd say 2007, even though there was a lot of stuff I didn't like about school in that year, my best friend who moved to Japan came back that year, and the best part is she moved into my apartment! If not that year than 2008 or 2009, I've made a bunch of friends in those years.