rotoscoping> I don't think rotoscoping is a bad technique per se. I played the old (DOS) Prince of Persia a lot and I still think the graphics fits the gameplay and mood perfect. So I think it's more of a misuse of the technique than the technique itsef (which noboy claimed here, but whatever

). Flashback worked great too, but I never played it that much like PoP.
About KOF. Personally, I think the backgrounds are way more ugly than the sprites, which I find just mediocre. There's a very interesting paragraph in "DOT creation":
Why construct a 3D Model?
Creating animation patterns for 2D characters was, until now, highly dependent on the skill of the artist assigned to the character. The results could often vary wildly depending on the animator, and to fix this, we developed our animation motions with 3D models in order to standartize every character's moves before anything else. This eliminates individual style differences among the artists and ensures a high level of quality behind every move in the character's skill sets. It also saves the artists from having to draw 2D rough drafts for every frame of animation. The resulting rough pixel art is extremly detailed but still far from original goals, so the 3D models are used primarily as a reference for animation and detailing.
First, let's divide the discussion into animation / pixeltech talk (just like we would critic an animation here on pixelation). In the quoted paragraph, they talk mainly about the quality of animation. If I interpret what they are talking about, I think they are right. Apart from creating coherence, "Tracing" over prerendered 3D Animation (from a decent animator), creates better results than "from-scratch" work from a bad animator. But in return, the animation is just as good as the 3D animator. And I think we all agree, that hand-drawn animation has the ability to create animation which has that magical feel, which most of the modern 3D stuff lacks (Of course, it all depends on the animator).
What I want to say is, that using animated 3D models as a base is a efficient way to produce decent animation without having very experienced 2D animators (which are probably rarer than 3D animators these days). To this point, I'm not talking about the polishing of the single frames, just the animation by itself.
So talking about the animation, I think they did a good thing (mediocre), but if they talk about godly animation, I think they don't deserve this rank. The animation is pretty stiff compared with older fighting games animations. Remember all these bouncing boobs in the SNK games back then (I'm not a supporter of bouncing boobs!)? In this KOF the boobs are nearly frozen. Well, maybe it's a stylistic choice (realism? Character design?), but I assume it's because of the stiff prerendered 3D Models. And maybe more eye-catching, the falling skirt, which behaves very unnatural for me.
If we want to talk about the pixelquality, I think they didn't do a very special job. I think they did a good job of producing coherent results (a coherent look over all the different characters). But pixelquality wise, I think the didn't paid very much attention to the single pixels. Banding is a term which was used very often. Another thing I noticed is the lack of antialiasing of
self-shadows. Why is that? It gives the impression of a fast rendering job by bad artists. Just like the color departement in the old animation films. Lots of people which colored the cells without thinking (because they are paid per cells and thinking reduces the output).
You can call me silly, but I state that it's possible, today, to code filtes/shaders that can render similar looking sprites from 3d models even on the fly. Think of "hinting" in Fonts these days. A similar technique could be used to prevent important details from disappearing. Other algorithm could be used to create nice looking edges and curves. The color quantization could be done on the fly or in preproduction by good artists. I don't say computers can create great looking pixelart, but they can produce mediocre pixelart on the fly which is probably similar to what we see in KOF XII (maybe that's a topic for itself, but whatever). To work 16 month on a single character of this quality animation-wise and pixel-wise is a waste of time and money imho (the used time is probably an advertising-lie).
But what bugs me the most about KOF XII are the fugly backgrounds. Okay, if they are 100% animated, everywhere, then maybe they have a reason to use a 3D base (but overanimated backgrounds would only be annoying, tho). The design is way to noisy for a background, the characters are fugly 3D-shaded puppets, the architecture is mostly boring and the mixture with 2D painted, 3D rendered and pixeled doesn't work as a single piece of artwork. Thinking of all these amazing pictures
fool has uploaded on pixeljoint lately makes my artist- and pixel-heart cry. Maybe they spent all their love and soul already on the genious sprites?