I already did this a few weeks back, but when I saw this contest, I immediately wanted to submit this to it, because I think it does show some great improvement.
2010 vs 2012
Edit: What's with all that crap people saying the first one is better? True... you might not like the new pose or composition or something. But from a strictly art-quality related few, the new one is way better. Or at least it has better colors and anatomy