The ones on the right have nicer-looking colours and better-places shadows than the ones on the left, but they also have such low contrast that a lot of the details are almost impossible to see, while the contrast in the originals is fine (a tiny bit low). So, you've improved in some ways, but taken a step back in others - perhaps because no one told you what you were doing well before!
You're using a lot of thick and jagged lines. When drawing a line,
don't double up the corners. I recommend giving the
tutorial I stole that image from a look, it has lots of helpful tips.
