Okay so this is a try from me for a realistic image... It's not the best there is out there but it's an honest try and I think it's not all that bad...
But I think you rather concentrated on shading the image than on the actually face of him. The shading alone doesn't make a picture good, it only adds more to the positive aspects. Maybe next time you could leave the shading for a little while and rather adjust the face (the nose looks a little bit weird).
As mentioned, I think the shading is very fitting and how about you smear the edges some more? It would give the picture more smoothness.