I played Ninja Gaiden Sigma's demo at my cousin's today. Not really impressed aside from the graphics. They sped the action just a tiny tad so it initially feels different, but any Ninja Gaiden fan could adjust easily.
It was pretty much the same thing but with brighter colors and a worse camera. I honest cannot stand the camera in Sigma. The camera in the original was annoying, but Black fixed it up a bit. Now, however, the camera auto ceners on Ryu and you constantly have to change the angle while fighting, something you don't need to do at all even in the original version.
Quite frankly, if you have already played Ninja Gaiden for Xbox there is little reason to check out Sigma unless you're a big NG freak. If you haven't played Ninja Gaiden, it would cost less to just get a 360, download the Xbox compatability updates and play Black. I'm still wondering why Team Ninja is even doing this project. Why release ANOTHER Ninja Gaiden update instead of just working on Ninja Gaiden 2?
The controls take time to get used to if you've put some time into the Xbox version, but for some reason they still don't feel as tight as they do with Controller S. Lack of triggers.
