Well, it may look better for some stuff, but I'm just not a fan of CGI in general, now that so many American movies seem to be relying on it for almost every little thing, these days.
However, yeah, a well done CG Ryuk would look good, but by well done, it would have to be much better than the CG Ryuk from the live-action Japanese Death Note movies. In those cases, I honestly felt that the CG versions of Ryuk and Rem looked like ****, even though I must at least give credit to them for looking like how they did in the manga, in terms of their character designs.