The realtime part is unnecessary though, unless you are planning live action motion capture.
I have been curious about 3D cel shaded anime as well, since even realtime is so close, actually better in many ways (better in the sense that if Naruto animators double, we will see something even more closer to Naruto Ultimate Ninja Storm, instead of cheap floating sprites for example).
Prerendered CGI shouldn't be any problem visually.
People may not know this, but Naruto anime actually uses 3d rendered scenes time to time, like a moving background from perspective camera, something like a tunnel or forest, and they almost always look out of place interestingly.
I guess the practical issue is still modeling and character animation.
There have been a couple of 3d celshaded anime also. Clone Wars was such if IIRC, there was also a shortlived MTV Spiderman show, but none looked like Japanese anime naturally.