The KoF style is much closer to a real life look than Capcom's style (more cartoon-ish).The way the muscle is shaded makes us think it faces us for the first part (nothing wrong with that) but then the muscle in the forearm doesn't look like a real one, you made it too big. And the hand shouldn't stay like that.
I tried making Luffy's head. One is more animeish but does not fit KOF style, while the other is more KOFish but, looks less like Luffy.
is a good start I recommend you this site http://2dwillneverdie.com/ have a very usefull tutorials and nice tricks if you want done pixel art in less time
The lower body is looking good so far. If you need help with the feet, I suggest you take a look at Joe:
