I was going to say I liked the style, but then I saw your reference, hehe
Well, I would say: You need a reference.
Even in traditional art, it is pretty common to do master copies, that way you can understand some of the subtleties of each artist, and get a little piece of what makes his/her art great. Just like Mega-Man.
But as you get better, try to start avoiding literal translations. That way you can maybe put the image you created into your portfolio.
Look at a real cloud, see if you can translate something that is not pixel art into pixels.
Compared to the reference, I would say you did highlights in the mountains that are far too repetitive (in angle and form) and that the mountains' colors are a bit too contrasty with the background. Maybe it also lacks some understanding of form for proper shading.
The contour of the mountains aren't too pleasing, and this is:
Partially because the lines are jagged (
http://www.minddesk.com/wiki/index.php?title=Classic_Pixel-Art_Basics_Tutorial)
Partially because of tangents (it seems like the top of the rightmost mountain is exactly at the corner of the page, for instance)
Partially because the countour looks undecided in one point (first valley from right to left)
But these tips apply to other things in the image that aren't as unpleasing as the mountains, like jagged lines in the clouds.
I hope that helps!