There's nothing wrong with having a bigger piece, you just need to be more aware of details on that size.  Bringing the size down did get rid of the readability issues (mostly clothing).  The items in his hand aren't as clear though.  Your work with 3D is very obvious in the shading.  It's good, but don't let it limit you.  You can have a lot more fun with artistic interpretation, and it's much easier to get curves.  The black outline is inconsistant, sometimes connected, sometimes not; sometimes colored, sometimes not.  Pick one and stay with it.  Very good for your first, lots of character.

I would highly suggest not using the same colors on the sprite as you do in the background.  Right now he looks like a manaquin or something that belongs in the background.

I'm assuming you did the work for everything on this city.  There are a lot of shortcuts with your pixel work, and it's showing.  The grass doesn't look like grass.  There are no blades, and the highlights are random blobs.  It might work as a dirt or rock tile if it was cleaned up a little.  Far too many things on this have noise or dithering when it doesn't need it.  The cars expecially.  I like the line work on the van, but the dither kills it for me.  It's supposed to be metal, go ahead and give it a shine.

It's very obvious what brush you used to make the pine trees.  I'd suggest looking at real pictures of trees and then looking at how other pixel artist you admire do it.  The other trees have a better shape, but since they use the same colors as the grass (or close too it) it blends in.  I didn't even see them at first.

The cement ramp looks pretty good.  It looks like it's made of cement, which I don't think I could pull off.  The inside needs more dithering to make it a smooth curve.  Right now it has a very obvious line.  With the other ramps you should try dithering it yourself instead of putting a gradient in, reducing and letting your program put the dither in for you.  Right now if it weren't for the black outlines they'd look like they were all made from sand.  Though the middle ramp isn't so bad.

The black outlines are random and a bit jarring.  You should pick one or the other.  Though it does look like they're only there for the WIP parts, which is good.

Those are the things that stood out.  A little work will go a long way with this one.  Keep at it!

The crystals are good, but they don't seem to match the style of the rocks.  They're a little too flat, and the outlines are harsh.  I agree with Xion about the grass, just a few tufts growing out of the cracks will look a lot better.  I also think the moss didn't quite work.  If it was near a water source or on all of the rocks it might though.