refine your outlines al little bit more.
bot arms look awkward, since they both have only 1 joint in different places (the wrist on the left, and the arm on the right. )
background and ground could use some shadows.

What kind of game will this be? I imagine it's a sidescroller, but what will it have to make it different from others, besides the charming characters, colorful designs, and fluid animations? 
This game HAS to be finished 

Looking good so far. The only problem with the HUD is it's hard to see. You could try outlining that and see if it makes any difference.

The sprites are good but the problem you've got is there is no interaction with them and it looks very disjointed. The main character is just standing there watching a barrel of fire and a supermutant's head just exploded for some reason. If you linked these all up it would really look good. I'd add more supermutants to this and give all the characters weapons too so it all fits together.

thanks, but like I said, the hud will be remade, and I'll change the player sprite to fit the scene better.
the sidewalks are pretty basic right now, I will add some more detail.

Sorry about this double post, but it seems no one cares 
Here's an update:

ignore the white space with the tiles.
the thing on the right will be the remains of a building, I will add a few more creature, possibly some scorpions, and I think I'll redo the HUD, since it was pretty ugly.
Oh, and am I getting the style right? cause I think that's the most important thing.