What does that even mean? Playing on the top two lines means nothing. Just being on the ice is what's important, and Staal or Spezza can be effective no matter what line it is. Here's a hypothetical I'd throw out. Two player, one gets to make the squad
Player A: Excellent defensive player, limited offense. Paired against the other team's top line, he'll generally shut them down. But he won't score at all either. Net resut when he plays: 2 goals allowed, 0 goals scored (-2)
Player B: Solid defensive player, but not nearly as a good as Player A. Very good offensive player, however. He will not fare as well defensively, but will score much more. Even when paired against the other team's top scoring line. Next result when he plays: 4 goals allowed, 5 goals scored (+1)
Which do you choose? Logic states you choose Player B, as he helps the team more, even though he's not as good defesnively. Yet, some think the team absolutely must have pure defense guys. Well team Canada does have pure defensive guys, they are called defensemen. For the forwards, I'd want the guy who brings the most to the table.