Not completely unpopular but that I personally feel just very stupid, SNK shouldn't have do the KOF XII sprites.
A lot of people loves does sprites, they call them beautiful and the best sprites they even seen but the thing is that the main reason why KOF XII ended being crap was EXACTLY THOSE SPRITES, they where too hard to do taking months doing a single character, and apart of that the sprites are made to be seeing in a big size (like how they are showed in KOF XII, looking like the old sprites of Art of Fighting), but when they where shrinked in KOF XIII they look very blur and bad (particulary the faces, most of them look ass).
I don't say that they should use the same sprites of all life, in fact I think it would be worse since it would make the game look lame even with great mechanics, just try to do sprites adjusted to their time and budget. Maybe something like BlazBlue's sprites that looks neat and don't take that much to develop having already in mind doing them in a medium size would not only allow KOF XII to not be KOF XII but also include those characters that where completely vanished just for the sake of have the classic dudes.