Things I personally would change (All imo ofc)
-Nose is to flat (make it more "longer"?)
-Upper cheek bones are coming out to much making his face look wide
Again, i haven't studied human face yet, and haven't modeled one... so I am not one to really say. I suggest looking at a lot of refs of heads and try to sketch out the bone structure of the head. Study that, and then you will know which parts are off because you have an understanding of the structure of the human face.
Maybe someone else can be of more help. :)