Hello. The good first: your pixelling technique is on a good path, though unadventurous in my opinion, but it seems that opinion that you should maximise the usage of palettes and aa where you can etc is not shared by fighter sprite entusiasts, althogether a different breed from general disciples of the pixel in that they're content to make art that looks like capcom or snk sprites. So that that as you will. You're well on your way to matching 1990-era snk style.

The bad:

It's very clear your anatomical knowledge is rudimentary, and you've successfully to degrees hidden this problem in your pixel artwork because it's low-res and the length of limbs more or less is correct on most of these. You need to study the underlying musclature that makes up the human body. Basically, you need to stop seeing a human being as a collection of vaguely oval shapes, and see under the skin. Where each muscle goes, how muscle ties under muscle, supporting bone. This is difficult, and it'll take intensive real life study, not fighter-sprite-study to come to terms with it eventually. And when you do, you will refine these skills endlessly for the rest of your life.

What you also need to do, is work on constructing a human being thusly, so he obeys some center of gravity rules and seems to have a real weight about him. Your figures lack balance and gravital center completely. Furthermore you should work on mesostructural proportion (how big a chest is compared to a limb, not just lengths which you've got ok more or less) and finally, you need to break out of the wooden poses you've got going here. I look at those and go 'what are they waiting for?' They're more dolls than they a re fighter sprites, they portray no emotion or character for each of the individual fighters, no pose for combat to speak of, nothing but an idle human dressed in designer clothing.

To do this, you should go to an art store and buy a book on the human anatomy. You should spend quality time with it for a long time. When you return to pixels your powers will have grown greatly. This is how you'll become better, in my opinion. If you just want to make vaguely snkish doll sprites, you're good to go right now.

EDIT:



I am by no means any master of anatomy, but this should show you how much effort goes into planning a pose realistically. I even make the center of gravity mistake here, this body is leaning needlessly forward (where i've mared 'bad!!') and the shins are too long probably... so on. This is where you should be heading towards.