The game hits the mark in terms of Samurai Jack authenticity. As he battles his archnemesis Aku, Jack acts and sounds like you'd expect Jack to act and sound. Only cel shading, rather than 3D RenderWare-ing, would have taken this over the top.
It needed more content and more effort. The mechanics of the game are good (for the most part) but the most impressive engine and artwork in the world cant make a game excellent without any substantial content.