His left eye is a little different from the right...the right seems to have a little more red in the brown (making the brown more vibrant) and the highlight is brighter, too. Just comparing the two, the right is more striking, and the greater color contrast makes it look sharper than the other.

The likeness is great, no question, and the skin tones work really well with the blue highlights. It's easy to overdo (I know that) and you have just the right amount, and the blue over the left eye carries it through very well and really helps define the eye shape.

I see the background is from a different painting...very cool, especially the closer stars in front of the nebula/gas cloud. And super bonus points if you did all of those pinpoint stars by hand...