So overall I think you seem to have a nice understanding of the proportions and placement of the feature of the face. I'd say that only the ears seem a bit too high for the angle you have and maybe the eyebrows are a bit too low.
I think one the main issue I'm seeing would be about the shading. It is too soft which makes the face look flat and lack dimension and also it seems like you used the same hue for the lights, midtones and shadows which kind of give a ''plastic,, look to the skin. When going form light to dark you also want to vary the colors a bit to give it more life. So if your lights are warm you generally want to go towards a slightly cooler color for the shadow and vice versa.
So for the softness problem, I usually like to start by defining the main shapes using a harder edged brush to really have a clear volumes and then I soften it as needed. Contrast is one important tool in art and having softer edges put against harder edges will just be more interesting. So first, I laid out the basic forms of the face and them used this as a guide to put the light and shadows.
And then once the rough block out is done you can start to refine things. One thing I'd say is for the eyebrows it's probably better to do the main rough shape you want and then add indications of hair rather that drawing all the hair individually like you did.
Sorry that he doesn't really look like the same guy anymore 
But hopefully this helps you a bit.
