I think it would be hard to make a multiplayer Metroid different from any other of the dozens of FPSes out there, since it's the exploration that makes Metroid fun, and I don't know if it's possible to fit that into a multiplayer experience. But then again it would add value to the game, since I'm sure there would be some people who would enjoy it. And I agree with gbafan that Nintendo really needs to get on the ball with regard to online multiplayer.