I think everything in this shows you have a solid understanding of pixelart and drawing. There are a few things that can get touch ups, some parts have banding. And that vine on the right looks mixed res almost.

I think the biggest and best change you can make is to readjust the contrast in your layers. Foreground should probably have the most contrast with atmospheric perspective getting strong for further layers.

Your zeboar has pretty good contrast, but your monkey needs those dark shades to get darker. Maybe.

Quick bit of advice, don't simply say you want to have 20-30 times as much art as another game. Go into a little more detail, do you have a lot of characters or environments. The characters in that style seem a lot easier to make than the environment. Something to consider.

I need to tackle a lot of the really big areas. Probably need to look at some reference because I'm at a loss for what to put in the background.

And this piece lacks a lot of cohesion. I need to step away from it again and think what I'm trying to convey.

Bit of tweaking. Mostly retuning the colors relative to the witch. Moving a lot of colors around still.

@Decroded: I'm not entirely sure what you're saying. I started scribbling out my palette on the piece now, finding better color transitions and unneeded colors. Down to 33. I'm sure I can get it to 32 with no issues. PJ image spec tool says I've got ~5 colors used less than 0.1 %

I keep getting lost in AAing things. Slowing down a lot of work, so I'm trying to just scribble things in and move on.