The new version of Ninja Gaiden look sooooooo damn good, this game is amazing. If you own a PS3 and if you haven't played Ninja Giaden or NG Black on the xbox buy this game without a second of hesitation. If you have the old games you might still wanna get 'em if you really like the game for 3 big reasons:
1. New playable character that you can also play on the demo in a survival mode kind of little mission (she is very fun to play).
2. Looks so amazing, might be the best looking game out on the PS3 so far (maybe Motorstorm looks equally good but I dunno), especially if you have an HD tv it will blow you away...
3. 3 new missions that were never there before and new weapons and moves, if you love Ninja Gaiden that reason alone is a pretty big one.
Me? I'm gonna buy the same game for the third time, granted it has more features. This game along with Resident Evil 4 and God of War (1 and 2) have probably been the 3 best games I've played since FF X ish times.
I've been playing the demo over and over and over again which I you might just not understand playing the same two levels so many times, but if you know Ninja Gaiden you know how challenging and hard (But fun) it is to go beat the levels and adding scoreboards for each difficulty and the Rachel stage was such a good idea.
This is easily the best demo of a game I've played so far (As in it comes with lots of features for a demo, different upscaling difficulties and a completely new area that was not in old Ninja Gaidens and leader boards that make the demo very competitive).
Right after playing this, I got the Virtua Tennis demo and I saw what a crappy demo is like, you play one like 5 minutes game and that's it... it looks like a good game though, but come on after playing Gaiden demo I demand a little more effort in game demos.
If you havea Wii and haven't played RE 4, get it you will not be disappointed. All of the games are violent though so yeah not for the kids.... (especially GoW and RE4).
Alright already posted too much, in short buy this or one of the Xbox Ninja Gaidens (less good looking but still best looking Xbox game ever maybe) if you don't have a PS3 and buy RE 4 on PS2, GC or Wii (When that comes out :)