It doesn't make or break the game, but New Game+ can be pretty awesome. In something like Dead Space 2, it's just an absolute blast to be able to go back through the game with all your stuff and full upgrades to completely murder all the enemies that gave you a hard time the first playthrough. It doesn't beat the intensity and tough choices inherent in going through the game the normal way, but sometimes having that kind of power from the outset can be fun.