Pretty awesome work, although just a few minor complaints:
Articuno's head looks incredibly small compared to the chest and stomach. It also appears to be off to our right a bit.
Entei's pose looks a bit unnatural, but other than that, it's fine.
There seems to be a random circle of highlight on Zapdos' head. I think it would look better curved, or without the highlight at all.
The hanging tuft of fur on Raikou's stomach looks a little long to me. I may be mistaken though.
All in all, pretty good work here. Keep it up and whatnot.