No, no- Ninja Gaiden didn't just "borrow" gameplay mechanisms from Devil May Cry, it WAS Devil May Cry, down to the fine little details. The biggest difference was the main character was a ninja instead of half-devil. I'm all for the spreading of gameplay mechanisms, but only when the developer is going to refine and improve that mechanism. Team Ninja just took Devil May Cry, made it prettier, changed the locales and character, and called in "Ninja Gaiden"- that's called ripping off.
And I love hard games, don't get me wrong, but only when I'm still having fun. Ninja Gaiden is difficult to the point where I have no interest in playing it. Games like Viewtiful Joe or Ikaruga are incredibly difficult, too, but not at the cost of my enjoyment. They're difficult in such a way that I'm encouraged to keep trying. Ninja Gaiden pissed me off, Viewtiful Joe and Ikaruga never did.
And besides all that, Itagaki is still an arrogant, pretenious ass- there's no two ways around that.