Your pixel art is very nice, especially the Arceus one -very nice concept. However, even on the Arceus (I'm aware that the background and whatnot are intentionally kept simple due to making Arceus stand out), the shading is still just a bit bland. Now, I won't say much, since I'm sure that Arceus was meant to look that way, but, maybe you could try adding at least one highlight color here and there? Who knows if it may make it better or just ruin it, but I'm sure it wouldn't hurt to copy and paste another one in paint and try, that is, if you wish. However, I still do like how the shading turned out on Arceus, and I love the lineart and beautiful pose. Arceus is such an awesome 'mon; so... mysterious. X3
Your revamps are also pretty good, but some could use some work, such as the Dewgong and Charmeleon; first of all, Dewgong... well, the shading actually turned out very nicely. However, it would look much nicer if you were to apply just a little bit of that highlight color to Dewgong's upper-ish body area; even though the lightsource is at the top-left, I would believe that at least a little bit of the "bust" area would still be exposed to the light. Same goes for the snout. ;]
Now, as goes for the Vulpix... it still looks a tad bit, well... "untreated", or unrevamped. As goes for the right eye (our left), it's missing a pixel of brown just above the white highlight. Now, for the left eye (our right), I'd reccommend adding a pixel of the brown used in its eyes just above the very left isolated-like pixel, the one on the very inside of the center-point of the face (if that made any sense to you, because I tend not to make sense XD). The shading on the right-lower area of the head also urks me a little; it almost looks as it it's "pillowing" (following pixel-by-pixel, in this case) the outline below it pixel by pixel rather than just... well, erm, I don't quite know how to really explain it right now, to be honest. o-o"
I honestly just think that you should re-look the D/P Vulpix sprite over, and fix any issues that you find to make the sprite look peculiar. I'm sorry I can't explain it myself right now; if I were, I'd be here for awhile, seeing how I have to go into so much detail with everything. XD;
Charmeleon... it definitely needs some black in its outlines, mainly where light hits it less. I don't think there's really much to say there. The pixels on the bottom of Charmeleon's tail also need a little bit of evening out....
Ugh, now I'm just getting plain vague. X_x
And also, remember: Charmeleon's eyes aren't red. In the D/P sprites, they're black, but in the Sugimori art, they're a grayish blue (with black still being the base, of course). I'd just suggest looking over the D/P sprite and the Sugimori art and, like stated before, edit things where you believe is necessary - where things may seem peculiar to you.
Sorry if I got a little lazy/vague at the end. Nonetheless, I hope I helped.
Oh, and I'm likin' the Sugimori pixel overs so far, by the way. I encourage you to keep up with the project. ^_~b