It's tough to show gender in small sprites like these, but if you really want him to look like a guy, it's best to do so through clues in his costume. The entire sprite looks pretty muddy and blurred, you could really benefit from reducing the number of colors, adding more contrast and more saturation. Don't be afraid of making bold changes, making outlines clear and showing where elements separate is the key to readability!
Look up "hue shifting" on wikipedia to see how your color choice could improve.