Well I'm not sure if this will help in your decision or not, but here's what Itagaki had to say about NG:Sigma:
http://www.joystiq.com/2008/05/21/itagaki-ninja-gaiden-sigma-is-no-good/
When asked about the game, Itagaki said simply, "It was no good." Apparently not into the whole brevity thing, CVG continued the line of questioning, prompting Itagaki to add, "Despite the fact that it's on a 'next-generation' console there's no evolution whatsoever. That was made not by me, but one of my sub-ordinates who basically tried to copy the success of Ninja Gaiden." You think that's pretty rough, right? Well get this: That guy was sitting next to him. And he was making Itagaki a fancy birthday cake. No, that stuff isn't true. But it's still fairly icy.
I need to finish up NG2, then I plan on picking up NG Black. Easy choice for me.
starcraft: "I and every PS3 fanboy alive are waiting for Versus more than FFXIII.
Me since the games were revealed, the fanboys since E3." 
Skeeuk: "playstation 3 is the ultimate in gaming acceleration"
