I think, if I recall correctly, that Sidonia no Kishi (aka Knights of Sidonia) is the only full-CG full-length TV series I’ve finished to date. I even watched the sequel! Now, I’m not sure if this means that Knights of Sidonia is a remarkably good show or that the other CG shows I’ve tried watching have just happened to be really bad, Sidonia was never the most consistent show in my opinion, but I can say that I did enjoy it from time to time.
Mostly, this was because of the battle scenes. From the very beginning, even back when the character animation was dodgy and choppy, it was obvious that a great amount of effort was put into animating the action scenes, and by the end of the first season I thought they were no less than fantastic. Also, I guess it’s worth mentioning that I thought the story and the world were really interesting. That kind of really-out-in-outer-space sci-fi is not that common, at least as far as I know.
Knights of Sidonia was by no means a perfect show, though, which is most clearly exemplified by some of the plot developments in the second season. In particular, I did not care for Tsumugi at all, and I thought what happened to Kunato was both confusing and ultimately stupid. By the end of Season 2 I didn’t really care about the story anymore, but at least the action still looked good. At least it had that.