just something i'm working on..

[Vipershark]

Oh, I didn't see that edit that you made.
...ignoring the "flawed" from your friend,



I'm going to assume that the reason for posting Akuma was so that your friend can show an example of what he's trying to emulate, but putting them side-by-side just shows how much better the official sprite is than your friend's.
For one thing, you've put twice as many colors on a sprite of similar size

and you've got redundant colors there like that tiny sliver of peach in the ear and the eyes. That one sprite with all the clothes on it is so obscenely ridiculous that I won't comment on it but apparently talking about color count makes people angry so I won't go into that anymore.

Regardless of color count, you[r friend] simply do[es]n't have enough hue shifting or saturation changes, and the contrast is almost nonexistent with certain shades.
For example, the two darkest blues are so close together that the darkest shade simply gets lost because it flat out can't be seen.
You might like it when the sprite looks like that and has flat colors, but that is completely wrong. That's not personal interpretation, it's wrong. Light is made up of an entire spectrum of colors and simply doesn't work that way.
Your friend seems to have a decent grasp on shading as far as the shapes and such that light makes, but his color usage is incorrect.
Let's look at official sprites that use dark colors. King of Fighters is a good example of a series with large sprites and lots of shades.

http://www.spriters-resource.com/playstation_2/kofxi/



Each of these characters is wearing dark clothing (Ex Kyo's pants are debatable but close enough) and yet they're still bright enough and have enough contrast that they're easy to see. I don't have to try to look for details because they're all visible. Even the Akuma sprite above (which, again, I'm assuming your friend is trying to emulate) does this.
Your colors are so dark and so close together that the just bleed together, which in your eyes might make it seem like they're more detail, but it actually has the complete opposite effect. Instead it makes all your colors just melt together into one blob of color and all the details get lost.
Contrast makes things pop out and look appealing. Lack of contrast does the opposite.