Ninja Gaiden will beat you mercilessly if you aren't careful.
First and foremost, NG is beautiful. I think it has the best graphics of any game this generation of gaming. Bad part is that you have to have an XBox to play it. But if you have one there's no reason you shouldn't have this game (unless of course you can't handle it).
Ninja Gaiden starts off training you...for about 2 minutes then it shows you that if you're not careful you're going to be dead really really quick. This stands true for the rest of the game. Regular enemies and bosses alike posses the speed and power to massacre you if you let your guard down. You'll need to be quick and precise to stay on top of these guys. Do not fear though, Ryu posseses the skills that he needs to do this.
There are plenty of different combo's available to you to use along with several different weapons to use for your different fighting style preferences. On top of that you can use karma that you earn to level up your weapons in turn receiving new moves along with buying new moves from shops. There won't be any button mashing in this game; the more of these moves you can master the more easily you'll be able to get through this game.
Bosses in this game are big and powerful and they know it. There will be some absolutely gorgeous videos to showcase many of them and they will each take a different skill to defeat. You'll have to watch and study their attacks and learn when you can/should attack them and how. Each boss will provide a new challenge for you and thats definitly a good thing.
The games story is a pretty good tale. I think with everything else being so excellent it kind of gets ignored. Especially with the beauty of the videos, you'll be watching in awe and the sound will just be tuned out (at least it was for me). Thats okay though, at least it doesn't happen on purpose.
The game also has some collectables spread throughout which will allow you to unlock the original 3 Ninja Gaidens if you collect enough. Thats a solid unlockable.
The only downside to the game I can really see is that because everything in the game is so smart that it makes it difficult and can be frustrating at times. Really though it's just a well made game. The difficulty can be overcome by mastery, which is how I'm sure Team Ninja meant for the game to be. Anyone with an XBox should definitly be playing this game. The end.