This is a LAAAATE reply (sorry for that), but might I say that it is also (most of the time) a FAIR but frustratingly-difficult game. Most of the time, it's you're fault if you die. I don't know if the Sigma has this feature, but Ninja Gaiden Black on the old Xbox (both of these games are updated rereleases of Ninja Gaiden on the old Xbox) has a feature that lets you freely control the camera if you click the right thumbstick in (this works pretty much everywhere except boss fights; you can switch between this and first-person).
It's a game where you REALLY have to get to know your opponents, who WILL kill you. A LOT. However, if you stick it through, you begin to learn things. You begin to learn what you can do, as well as what your enemies can do and how they behave. Once this happens, you will slowly begin to kick more and more butt, and you will get to where you are just being invincible, tearing up hordes of enemies like a BOSS.
TLDR: My biggest tips of advice for you are A ) study the nature of your opponents CLOSELY. B ) If you are having trouble with the camera, try to see if you can click the first-person view stick to change the camera control to third-person. C ) BLOCK AND ROLL. Even when you are in the middle of the sickest combo, hold the block button. Seriously, this makes it so Ryu will react fast enough to stop attacking and block an attack, even if you are attacked from the back. If an enemy attacks with a block-breaking strike, block but then roll AS SOON AS the strike hits.
If you need further help (or just didn't want to read any of that), try to get some knowledge out of these videos that I made. Pay attention to how I move (though I certainly do NOT claim to be a pro), and in the case of that first one, watch how the enemy moves, too.
