The difficulty was part of what made it so good. During the first level, there are these white ninja's, and the first couple of times through they pretty much kick everyone's ass, and everyone gets frustrated and they toss the controller around. Then, much later in the game, there's a certain part where you're in a hallway and quite a few of them keep coming at you in waves, at least 20 in all, and most people by that point can totally destroy them, they don't even get touched. Stuff like that was part of what made Ninja Gaiden so great in the first place. Playing it on "easy" is like playing a game on God mode IMO, it ruins the fun.