I'd say either Pittsburgh, Detroit, or the Hawks.
Pittsburgh has good depth and the best player in hockey. Plus, Fleury was fantastic. They also went back to back.
Detroit went back to back in the finals also. They had a great goalie in Osgood. Lidstrom wasn't as old and was fantastic.
The Blackhawks had probably the deepest team I've seen in years. All four lines had very skilled players and they had great defensemen. Their only fault was that they didn't have a great goalie. Niemi proved himself by playing really well in the playoffs though.