This is amazing.
The colors you use apply very well to the orignal Alien Hominid, also the fact that you decided to throw in some nice anatomy instead of making him so plain is also a plus. However I've always pictured him as more of a chubby Alien and not so built up, but like you said you did it your own way, so there's no way it could be incorrect. I like the color and way you did his teeth, and his eye is just so well shaded to portray that he's still in fact just a cartoon in a way and not exactly so realistic. The gun itself could've used a little more work, but I understand your main attraction point here was the character himself and you still did a good job on it so props to you on that.
What really caught my eyes the most was the shading you use, it shows a lot of the skin complexion and how rough you imagine his skin would be, and that my friend, got your point across really well. Looking at that, in a way, scaly? Not exactly scaly but rough, skin, you get a sense of what his complexion would be like. You did an excellent job my friend, and you get a 9/10, 4/5... I would make it 4.5 but I can't. And I don't want to make it a 5 or 10 because I don't want to seem like I'm sucking up, and nothing's perfect.