Easily NG II.
Dark sector is fairly run of the mill and the aiming stinks.
Ninja Gaiden II is a way deeper game that as you learn it you become more interested and immersed into. The only issue is really how the camera acts sometimes. But, it is essentially a game like Devil May Cry 4 that allows you to change the camera as you see fit and doesn't lock in to a specific angle for each area you go to. And the game as a whole is way tougher then Devil May Cry 4. Especially, the boss fights.