Your sprite has pillow shading, which is something you want to avoid. You can see it most with his pants and boots. The shading with his arms is pretty good. Face needs more love. Face and eyes can be rounded to give a more natural look. Hair is pudgy.
The character's concept art is really well done with his hair and head. It should not be too much trouble translating that into pixels.



My edit with the corrections. I just restarted learning about clothes so anything with them that I make tends to be rather weak (illogical wrinkles, simplistic shading, etc). Someone else on this forum should be able to help you with that along with the perspective and shading you are going for.