After looking through your art work, I seriously think you often do a good job at doing the poses and could imitate the art stlye of Akira Toriyama really well.
The sketch really does reflect everything about Goku. It shows that he's cheerful based on his expression and the ragged clothes combined with his expression shows that he loves to fight and is a person determined to train harder. Just form his pose and expression defines who is Goku along with great details.
Overall, I think that this sketch is great because of how it not only looks good, but how it defines Goku and it gives me some emotion and feelings.