It's slowly getting there... I don't think it's in keeping with the standard RTP sprites... But I think with a little bit of time you could make it much better.
I think you sticking to the Primary colours has made it look very childish and overly cartoony... For example if I was making it (Now with my experince) I would make it look much darker, and drab... Those vibrant colours just look wrong for the era of the game sets... Way to modern... Looks like some thing out of a Nike Advert... The Black key line around the hair on the walking Up state is a litle in your face, makes him look like he has a Lump in the back of his head...
But your shading is good, it's all about right, the swapping of the knee pad is correct and in keeping, the animation is nice... For your first sprite it's good.
Here's my first ever scratch build:-
It's funny I made pretty much all the same mistakes when I started out, looking back at my first one for me is slightly embarrasing now... I think now I am creating some brilliant resources... like me you should Keep at it, I think you have potential, you taking constructive critisum well... Gilgamesh Gave me some brilliant pointers when I first started out !!!