Awesome model
The skin is very good, I can't see anything wrong with it, it makes it look just like him.
But there are a few things about the model you might want to change, just some proportions.
The hands:
While well done, don't really look like Buu's because in the show his fingers were pretty short and stubby compared to that of a humans.
The arms:
Are look too thin, like bombsquad said.
The waist:
Again, this part looks to thin for the model
The legs:
Does the model look different/better iingame when the legs are shorter? Is this compensation for a "fish-eye" effect?
If not, then you might want to scale the legs vertically somewhat, because they're far too short for the rest of the body.
The feet:
Like the rest of the lower part, it's well modelled, but out of proportion.
Er, one final detail, not really neccesary, but he doesn't much in the way of a backside
I hope my comments help.
Btw, how many polies is it?