Amazing aa and dithering. I think compared to the original, your version looks slightly more cheery, while the original has a sly...sinister feel to it, but I think it works both ways. As for the colors; I prefer yours you Helm's, because yours keeps that cartoon-esque look, where Helm's borders realistic.
There's really only one thing that glares out at me, and its the highlight on the cheek; the yellow-orange's undithered edge seems a little too harsh, though you may have it that way to give the cheeks a sense of chubbiness....I'm really unsure how you'd address it, but, to me, it sticks out.
Great progression though, from photoshop'ed doodle to pixel art, and good work not just posting the color reduced version
(though I'm sure you'd never do something like that)