My vote went to Morrowind my favorite of the elder scrolls games and the only one I got super into. The scope of this game back in 2002 was simply nothing I ever experience in a RPG before.
My runner up is Neverwinter night more because of the moding then anything else. This is probably the first game I spent more time playing user made content then the actually content released with the game.
Dungeon Siege would be my third place game of the year. Fun action RPG.