IF I had one line to put out against any line in the league right now it would have to be The Richards -Hartnell combo in Philly. Not sure who exactly is the other winger is going to be but in just those two you have 60g, 140pts, 206pim, and a Selke nominee.
You put a healthy Briere or Gagne on that line and the offensive potency goes through the roof. Put a tough defensive grinder on the line and you have about the best shutdown line in the League, that will even kick your @ss and score a goal or two on you for good measure.
Sure Datsyuk or Zeterberg may be better offensively and defensively than Richards, slightly on both counts, but Richards has a toughness neither of the Europeans possess.
I don't know about the BEST line in Hockey, but this one is fast becoming my favorite regardless of the 2nd winger.