Ryu Hayabusa's totally into cutting fools into ribbons. Ayane should work in the meat industry.
Ninja Gaiden 3: Razor's Edge really is a totally different game than Ninja Gaiden 3 (which GR gave a 2.5). It's been completely retooled—from the difficulty, to its point-based leveling system, to the degree of violence and dismemberment (there is a lot of it), to the inclusion of Ayane missions in the single-player experience.
In Ninja Gaiden 3: Razor's Edge, you play as Ryu Hayabusa, a ninja master who—blah blah blah—someone is trying to make a God-thing and there's bad animé-esque voice-over to fill in for the pathos. The story is somewhere between a lesser Resident Evil and a Time Crisis game.
This doesn't matter because the gameplay is [expletive deleted]-ing awesome. Hayabusa rips from one enemy to the next with body-dismembering glee in a glorious sword-driven blood ballet; well, until an enemy hits you. Then you're screwed until you block or dash away. Because the game is frickin' hard. The difficulty is slightly mitigated whenever you have the opportunity to level up your weapon, but enemies are soon replaced by a new breed that's wise to your prior set of tricks.
The difficulty level of Ninja Gaiden 3: Razor's Edge is ridiculously intense. On normal mode, it took me an hour a piece to beat several of the bosses. There's a point where I know that a game and I have issues. In Ninja Gaiden 3, I knew the boss fights were too difficult for me, when I started to get worried about wearing out the buttons and sticks on the Gamepad from pushing too hard. Keep in mind, this is the first game I played on the Wii U.
There is one boss fight early in the game, in a new level where you play as Ayane, that was so ridiculously hard that I had to change the difficulty level from Normal to "Hero", which is a no-fail mode. (Don't judge me.) I switched the game back to normal afterward, when the game picked back up again with Ryu's story, only to find his section ridiculously easy by comparison. The difficulty can be erratic, to say the least.
Part of the problem is Ninja Gaiden 3: RE's camera. It automatically flips around to try and keep most of the enemies in view. You can switch to controlling the camera manually with a button press, but then moving the camera requires you to remove your thumb from the attack controls—a recipe for instant death.
The other problem is that your ninja master will auto-target whatever enemy is closest at the end of a successful combo, which can sometimes include enemies that are off-screen. In general this is extremely frustrating when you're trying to target a specific enemy type with an attack that is particularly effective against them, only to find yourself clubbing a grunt.
This is not necessarily a deal-breaker. Because of the intensity of the gameplay, if you're surrounded by enemies or too many of them are tweaking the camera, you probably need to dash away to the edge of the fight (since you'd probably die anyways). However, it still is really annoying, especially when a large number of combatants are in play.
A huge part of success in the game is timing your strong attacks to hit during an enemy grab-attack attempt. Do this and your ninja will erupt into a death dealing chain of attacks that has the potential to cut every enemy nearby in half at the waist. With Ayane, this occurs with such precision and fury that the enemies are reduced to butcher-sized chunks of meat ready to go on a ninja cannibal's barbecue.
The karma system now includes a multiplier that ramps up continuously the longer you chain attacks without using Ryu or Ayane's special attack. This increases your point value, which allows you to buy new techniques, weapon proficiency, and ninpo (ninja magic).
Multiplayer seemed largely the same as in the PS3 and Xbox 360 versions. Players can sink a lot of hours into it, in order to level up their faceless ninja into a customized badass through challenge areas that can be played co-op and clan-based PvP battles. The game doesn't do much to utilize the Gamepad, and it looks like it's been optimized more for the Wii U Controller Pro.
In short, if you're looking for a hardcore Ninja Gaiden experience from Ninja Gaiden 3, complete with ridiculous bloodletting and a very challenging difficulty, this Wii U version is your game. However, the inconsistent difficulty and poor camera hamper the experience, somewhat.