Lookin' good, there.
The blocks don't quite seem to be 3d themselves, but the crumbling edges define the shape they make up as a whole as 3d, so that works out just as well.
Those edges are great, by the way. You seem to have a real penchant for making tiles irregular enough so that they don't necessarily need variety tiles to mask the grid. That ladder especially. It's so wonderfully asymmetrical, I seriously had no idea it was one tile until I deconstructed it to start editing.
I didn't do much to it, just cut down some of the shadows a bit, applied some nonintrusive AA here and there, and AA'd the bent rung to smooth it out a little.
I also removed the 1-pixel dithershading on some of the rungs, because pixels in groups of less than two end up making shading look sort of noisy at this resolution.
On an unrelated note, I did up a run cycle to sort of demonstrate what I meant about side-facing animations. I don't know if it looks childish enough for the character, but I gave it my best shot. (It's on a black bacground because I had to use some AA for more subtle motions and it doesn't show up well against Pixelation's grungy green background.)
Also comes in grizzled war veteran variety (to see the legs and torso more easily)
Looking back, I didn't add enough bounce, the arms pretty much suck, and the whole thing is pretty stiff looking (and that's without mentioning that I mirrored the animation).
But, it gets across the general idea, I hope. The only reason that I think side-runs are favorable to 3/4-runs is because in platformers, 3/4th runs always make it look like the character is running diagonally instead of side to side, and it always seemed to me like they might run right off the side of the narrow platforms that all side-scrollers are made of. Just my two cents.
Edits 'n stuff aside, I'm curious about the role of the main character, the kid in the yellow raincoat. Who is he, and what does he represent?
Is he a god-like figure taken physical form, a la Ameratsu from Okami? An avatar of some sorts? Is the sun he's representing even spiritual at all, or is it just a ball of flaming gas?
Does he derive his power from the sun, if he has any? Is he bringing light to the world, like a manifestation of daybreak? If so, why? Does it happen every day, or is it something more heroic, like a sacred duty to bring light to the world after it has been swallowed by darkness? Does the moon make an appearance? What is the significance of the raincoat? Is he chasing away a rainy day?
I'm sorry for bombarding you with all these questions, and I don't expect you to answer all of them, probably in order to preserve the mystery for the actual game. Just a bit of closure, about why he is the sun, and why his raincoat is yellow.