The dark one's much too dark.
... generally I'd say the anim's ok. But, I'd be inclined to not have the arms swing like it's running a sprint - isn't that a gun/rifle it's holding? Surely it wouldn't be swinging it madly like that? Plus, the way it reads righ now makes it look like his arms are mutating in front of him in a pointy thing ... it's just weird.
I suggest to try doing it so that the gun is held in front with both hands... keeping it fairly static in front, but jigging around with the general motion.
The legs ain't working for me neither. You've got the characters foot impact point being beneath him, where it should be out front about 8 pixels from center.
Finally, you're doing the classic animation cheat of 'just' doing a four frame loop for one leg and then using the same for the other... there's nothing wrong per se with doing that but there's one thing you need to do to make it read llike two legs instead of one leg phasing with the other... actually there's two tricks, one you've picked up on (changing the shade of one of the limbs) the other... is to simply offset them in the frame by a pixel or two. This would mean a slight re-edit in this case to make the character more 3/4 view... but if you look at a great deal of other successful character animations ranging from Mickey Mouse to Mario, they tend to be slightly rotated to the veiwer for this reason. (and the fact it's more asthetically pleasing)
So. in a nutshell...
1. Arms, keep them fixed in front, with slight jiggle movement
2. Legs, offset them in the frame by a pixel or 2
3. Legs, Point of impact for landing foot should be a good 8 pixels from center.
That may help... if in doubt... read my post
on this thread. It may come in handy.
Cheers
