P.S. I checked out your Spawn piece and it's pretty damn good. A lot better than anything I could do in that kind of genre.
Anyway, I'm no expert and run mostly on instinct, so I have no idea if what I'm saying is making any sense. I hope I helped a little, and good luck with everything.
Thanks for the message in my profile.
I don't know about levelheaded, but I try to approach crits from a logical point of view and leave my ego at the door. It's the least I can do for people looking for a reasoned, objective perspective on their work. You probably know more about oils than I do if you've used them before. I've only used them a couple of times so my experience is more with acrylics. But I checked out your oil painting of the Titan and while it's a good picture, it seems to suffer from the same light problem as your digital.
I wonder if the mistake you're making is being too dramatic with your light and also your colour choices. Maybe try working purely in black and white for a while, and go for a more subtle light effect that uses softer gradations from the darks to the lights. And also don't be afraid to throw shadows onto things and use them to show the light source, rather than highlighting everything which is where that plastic look is coming from I think.
You're very welcome!