It's worth spending more time on the eyes than anything else - sounds wierd, but a good set of eyes will make a character seem real more than any pose or body texture or subsurface skin effects or hdri lighting rig. Without depth to the eyes, there is no perceived soul and so subconsiously we automatically judge the render defunct.

I'd also recommend that you don't compare your eye renderings to other people's renderings - compare them to photos and try to recreate actual eyes. Not that I've got it right or ever will, but it's fun having a good go.