The forums have a feature to zoom in to images on click, check this out:
Here, I pretty much regurgitated what I learned from my landscape studies in this quick and dumb edit. If you have the time, check out some real landscape photos.Maybe it looks fake because the mountain is artificially large and close? Maybe the colors don't reflect its intended distance? The flat side-view ground made me think that the mountain should be super far-away because the hero is standing in a flat plains area.
It could also look fake because it lacks a lot of finer details of a real mountain. If you try to fake details that you never took the time to learn, you're pretty much relying on cartoony shortcuts. Look at a mountain, draw what you see, you'll get familiar to all the small things that makes a mountain look like a mountain.