*edit*
I've recently purchased and played through half of the Vita version, and to anyone interest in it, don't get it. While framerate retains 30fps throughout most of each stage, there is significant framerate issues where it will lag at atleast two sections in each stage if not more. I've made it as far as stage nine where the game becomes unplayable as the game lags almost 100% of the time. In what might be a futile attempt, I've emailed Tecmo Koei and told them they owe me a refund and a prepaid box for return shipping to them.
---
This review should apply for PS3 and Vita versions of the game. The PS3 version in native 1080p though and has screen tearing here and there though which may or may not be in the Vita version.
Ryu Hayabusa meets and saves yet another big breasted heroine to learn that the greater fiends are attempting to revive the archfiend. After returning to his village just in time to find it being attacked and an artifact stolen, he goes after the greater fiends at his father's request. The storyline on Sigma 2 is even worse than the original as they force more storyline on you by trying to add personality to the fiends that you're fighting. Exclusive to Sigma, Momiji, Rachel, and Ayane are playable in their own chapters, but after that, aside for an item that Ayane gives Ryu, they disappear like ninja from the rest of the game.
The combat on Sigma 2 in comparison to the original has some changes that are for the worse, but overall it's been much improved. While the Dragon Sword is still the best weapon, there are altogether eight weapons you can use. All recurring weapons have been reworked while new ones have been added, and most, if not all, are actually useful this time around. My favorite weapons are the Falcon's Talons, which are mostly close range, but there's the dive kick and slide kick that quickly close the game between opponents and can lead into other attacks. Momiji, Rachel, and Ayane's inclusion in the game offers their own weapons and combat unique to them. Health has also been reworked as well in that every group of enemies you defeat, your health will refill, but the more you take damage, the more you'll become wounded and your health will be unable to go above that point until you receive health orbs or use a recovery item that recovers into the wounded section. While the health regeneration does make it a slightly easier on normal mode, on hard mode, you're always inching a victory just to get your health restored without using an item, hoping the last enemy drops a health orb so you can recover some of your injuries as well.
Regular enemies and boss battles have been improved as well. While most of the game you'll see the Spider Ninja clan variations there are a lot of different different enemy types in the game. Regular enemies also have a decent amount of health so they won't go down in just a couple hits. Enemies can also get their limbs cut off allowing for an execution to be preformed. When an enemy has a limb cut off, they'll start acting more aggressive and even the way they fight can change a little. You might have a ninja with both of his legs cut off, using his swords to pull himself closer to you, only to grab you and perform a kamikaze attack, killing himself while damaging you. Bosses are more enjoyable to fight as the game will allow you to attack and damage them at any time, rather than require you to adhere to their terms on when you can damage them. Some of the bosses attacks may give you a better oppurtunity, but they can be damaged any time they're not guarding and won't have some ridiculous auto guard or auto evade unless you use the flying swallow.
I've played through level six on the hard difficulty, Path of the Mentor I think it's called, and the difficulty really does increase quite a bit. Depending on the enemy and attack that's done, 25-75% can't be recovered unless you use a restorative item, a save point, or recovery orb, enemies take off twice as much as they do on the normal/warrior difficulty, and instead of the spider ninja, you're fighting versions of them with guns and rockets at the very beginning or a third reskin of the fiends you come across. Check points are at every save point or boss battle, and if they weren't available, I don't think I'd have passed the second stage.
While the combat is much better all around, the maps themselves are no longer interconnected and now broken into separate stages. Each stage is varied as they're completely different environments, through the various stages there is slight exploration with some health pick ups in chests that are off the the main path, but each stage has Ryu traversing from point a to b, which the next portion will be blocked off until you kill whatever enemies the game wants to throw at you. Ryu's ninja skills are still used to get around from time to time, which does break up the monotony and is somewhat prevailant in a few stages, however, there are stages with long stretches of fighting enemies, then it'll let you advance only to fight more enemies, with less unique traversal. Every one of Ryu's ninja skills are used in later stages but there's one form of wall running that they call the art of the invisible path which you'll use in the third stage and never again is that type of wall running used..
The game looks good, colorful and has a clean look to it, but textures are lacking in detail. It's really not pushing the current gen hardware. Aside from the native HD resolution, the enemy count, the cutting off of enemy limbs, and human enemies remaining on the ground, which would require a bit more powerful hardware, the levels feel like they could have been developed for last gen hardware.
Ninja Gaiden Sigma 2 will take 10+ hours to complete on normal mode. There's little to offer other than the games combat, but it's combat is some of the best the stylish action genre has to offer. It's a good game and highly recommended if you're looking for combat only and little else. If you're looking for something a bit more varied, there are other games that I'd recommend beforehand.
Gameplay-9
Story/Presentation-5
Graphics/Sound-5
Balance-7
Overall-6.5
New scoring criteria.
Gameplay - 9
Design - 6
Presentation - 7
Balance - 7
Overall - 7.25
Currently Online 
