Hey... i dunno if u remember me, i did a few sprites for u like 2 years ago :P
Couple of things your gonna need to work on, so i'll give u a list below:
1. Fix the outlines. Try to keep the outlines just 1 pixel thick when you're spriting. Try to get the lines to look smooth before starting to add color.
2. Shapes. The shapes you've used are very haphazard, try to get a bit of uniformity. Make the curves smooth, the head shaped more like a head, etc.
3. Shading. Most colors on a pokemon have 4 shades: Highlight, Base, Shadow, Outline. Keep the light source in the top left corner and add shading to make your sprites look more dynamic. Also, black should only be used to outline the darkest places of the sprite.
Try using parts of the official sprites so you can see how they make certain shapes etc. Also read up on some spriting tutorials and try to do some pixel-overs... they really help. And keep practicing... thats the most important part.