Of the two layers of platform-like dirt tiles, the foreground one is so much simpler and more primitive than the background one (strict squares and flat platforms vs. continuous surfaces with slopes and semi-natural shapes) that it doesn't belong in the same game. I don't know what character movement are you planning to use and whether you want slopes or staircases, but you shouldn't use both.
In many platform games there is a functional second layer of platforms above the ground plane, often special objects like buildings or trees (e.g. Metal Slug); in many games one homogeneous layer of platforms is enough because platforms are placed at any height and above one another (e.g. Bubble Bobble, New Zealand Story, Boulder Dash).
The simple square tile style can be enhanced with variations and decorations, with vertically linked grass tiles for the common configuration of stairs with grass above grass (it shouldn't look discontinuous), and with softer edges in the dirt part, but eliminating the sloped tiles that make it look cheap by comparison would have the greatest benefit.
If you choose the sloped tile style instead, I think you should improve visibility of the platform profiles with thicker grass and undergrass borders, up to the size of the exaggerated ones you have on the square tiles.
