To start with, Ninja Gaiden II is quite possibly the most impressive game ever created if you only play/see it for 2 minutes. Without even trying, heads start flying all over the joint and elaborate finishing moves are conducted without even knowing that you actually did anything. In short, Ninja Gaiden II succeeds where the first games fails. It makes you feel like a badass ninja right from the outset, rather than viciously punishing you for the first 5 hours.
A long held adage in game design preaches that a game's controls should be easy to learn, but difficult to master. Ninja Gaiden II could be the poster-child for this saying. This is a fantastic quality of NGII's design.