Such high emotions over this game.
I can say for myself I do like XII. It's unfortunate for all the things it missed in terms of being complete (a boss, story, etc). I could probably name more cons than pros to this game (most of today's fighters I can do that with too), but the pros outweigh the cons for me. What it did have made it worth playing in my opinion though, which subjectively includes gameplay, graphics, and overall balance. What still makes it fun to play is really how unlike all the other KOF it is. It was experimental, and we all know the results, as well as measure them differently. Chargable and comboable CD, Clash, zooming, the risk/reward blowback. If XIII had the same systems, or gave the option of them, then maybe I'd never play XII again (something I consistenly question in SF, minus the ability to patch today).
The sprite work and detail of the characters to me are awesome and better than other fighters because not only of how smooth the animation looked, but it seems like there was more personality in everyone in XII. The different stances, taunts (animations often part of their special moves), and even moves reminiscent of older games. As many as older KOFs, no, but still pleasing in the new format. And somebody somewhere once described XII's character sprites as unbelievably balanced in terms of their bigger size, yet how fluid they moved and could combo, which I agree with every time I go back to play it.
In terms of music, I really don't like when the bgm's are stage specific (some of the remixes for the stages were nice), but I do prefer character-specific. However, custom soundtracks are the next best thing, especially when you don't like what's fixed on the disc. And I will miss the VA for XII's Raiden (who also has done Heihachi for most of Tekken).
Online, yes it was bad. Playable at one point for me, maybe before it became input lag, but bad a lot. Oddly enough playing a lot of latin players in lag who were pulling off combos easily made me get better in input lag, even helped me to correct things I'm doing offline (that ever happen to anyone else?). I'd join the rest of the people complaining about how unacceptable it is if every other fighter had good netcode. If only online could be just as good as offline; maybe someday.
And correct me if I'm wrong (seriously, and with evidence), but if not for XII, would we be getting what we know is XIII this October? They needed capital to eventually give us what what XIII is, they gave us a game completely experimental, in sprite-work, graphics, gameplay, and on next-gen systems. We as fans said keep the sprite work and graphics, and nix the rest; in-fact, how about a game based off an old and popular game like 98 or 02? Our feedback gave birth to XIII, and I think it was worth it.