This one's tough. Really tough. Start a team with Gordie Howe and Bobby Orr, or start a team with Wayne Gretzky and Mario Lemieux.
Old: Nighbor, Morenz, Cyclone, Rocket, Shore, Harvey, Hull, Mikita, Sawchuk, Plante, Beliveau, Red Kelly, Potvin, Robinson, Bourque, Esposito, Bobby Clarke, Lafleur, Trottier, Bossy, Tretiak, KLM, Fetisov, and funnily enough Messier
Quality of defensemen really sticks out here.
New: Roy, Hasek, Lidstrom, Crosby, Jagr, Ovechkin, Malkin, McDavid, Kane/Toews, Lindros, Forsberg, Hawerchuk, Sakic, Yzerman, Robitaille, Chelios, Pronger, Iginla, St. Louis, Chara, Keith, Doughty, gotta have Fedorov/Mogilny/Bure, Kariya, Selanne, Joe Thornton, MacKinnon
The older team looks a lot deeper which makes sense, as they have more actual years to build from, and they have already finished their careers. Who knows which of today's players will finish in the all-time realm, as we certainly have potential with guys like Pettersson and Dahlin. The younger team would rely on Gretzky and Lemieux to do some heavy lifting, which they are certainly capable of doing, especially if surrounded with this kind of firepower. But, I think the d-men of the older team create too much of a gap to overcome. Names like Orr, Shore, Harvey, Bourque, Potvin, and Kelly are a bit much for the younger guys. Older guys by a solid, but not large margin if that makes sense.