Just wanted to pop in and throw my two cents in with bengoshia. You were really making some nice progress on the sprite as it was (smaller). Making it that much bigger is seriously going to more than quadruple the workload across the board, for really no aesthetic gains. If you're going that big you may as well just go 3D.
I'll give you some harsh critiques on the big guy anyways, just for kicks and giggles:
His belt-line is curving really strangely, as if his pants are falling off in the back or his shirttails are not tucked in.
The close arm is really wacky looking. Can't really tell what's going on there, especially the chunk in the crook of the elbow.
Far arm seems to be nonexistent. We should be able to see at least a bit of his elbow I'd think. I also can't figure out where the hand holding the barrel of the gun is supposed to be.
Boots are not uniformly sized.
The shading on the legs is rather odd. Close leg highlight terminates well before the knee, which is odd.
His butt seems to be a bit droopy, though this is also accentuated by the odd curve to the belt.
The far upper leg is rather misshapen, seems to bow in at the middle, rather than out.
Anyways, I was really liking where this was going at the smaller scale and I don't think making everything so much bigger is a good idea at all.