Everythng looks better in the Manga.
I find it OK, but also didn't convince me to 100%
But if you saw the previous ending of the Naruto Anime, you saw the animated version of the Kyuubi Mode and I think he'll always look like it, a single 3D person in the whole Anime would be strange, even for the animators who seem to ignore many bad things in their animation.
the anime did it more than perfect. the manga is not even colored. what you have posted is a fan art of what it could look like. but animation is professional and colored to how Kishi wants it. with the added effects it is perfect and of course it will look like the game, in fact it is the game that looks like the anime.
if it wasnt for anime we wouldnt know what the manga would look like in color or animated.
I think it looks they way it's supposed look. It looks like the took the direct page from the Manga & animated & colored it. I don't know what you where expecting but it looks fine to me. & plus I think it will look even better once he uses it in a fight.