I wanted to use Gameboy's Mario sprites for my SMW hack, but SMW only allows Mario in a 16x32 grid with few exceptions, so I had to edit them. Criticism etc. is kindly requested as I'm not particularly good with spriting animations. Or people.
Hey, those are pretty nice! I can tell they're an edit of Superstar Saga sprites, as you said, but you pulled off the reshading excellently. Really well done. My only suggestion would be to work on the jumping and sitting sprites a bit. Mario's legs look way too short on the jumping sprite because the hat takes up so much vertical space. Try shortening the hat a pixel to see if you can free up more room for the legs. As for the sitting sprite, try taking off a pixel off his gloves and put his knees up, like this, except without him holding them:
Looks good. I would consider taking out the pupil in the eye and leaving it a solid black, or shading the face in a slightly darker tone in order to contrast with the eyes just a little bit more.
The walking animation is something that sticks out to me the most ATM, so I'll just comment on that. I know how hard it is to try to make such an animation more dynamic with a mere 16-pixel width to work with, but I still think the arm and leg movement of the 2nd and 3rd frames need to be more different from each other. Also, the animation would look better if Mario went lower by a pixel for each frame into the animation (or at least for the last frame). I probably worded this horribly, so if you need me to try and explain this again, let me know.
Also, if you're interested there's an SMW patch that allows for Mario to have 32x32 sprites on SMWCentral.