How to improve
You already have the first thing: You can make good melody lines and you have timing.
Second you can add a beat or a backup instrument like pads, bass and that kind of things. also you can add automation clips and whooshes...
Please check out my songs:
http://www.newgrounds.com/audio/liste n/ 462955
http://www.newgrounds.com/audio/liste n/ 462190
(REMOVE SPACES)