I think Ninja Gaiden will have a batter chance in Japan and Europe, since it was an Xbox exclusve. The Japanese market never got a chance to play the game considering the Xbox's low market share.
Ninja Gaiden XB Tecmo 66,713
Even in the American market it would have sold about 800,000 at the best,
Year 2004 sales were 500,000+, lets say another 300,000 in the rest of its shelf life.
I dont have euro sales, with me but I dont expect the game to have broken 300-450,000 in europe.
Ninja Gaiden Sigma will do better than the Xbox iterrations in Japan, might even hit 400,000-500,000 in its lifetime.
Heeeeyyyy!!!! <Snap>