Sounds pretty good. I know I have the same problem when I write my pieces in MIDI format, The least you could do is add some dynamics, change the volume levels. Also, it could have been better with some good panning, I'm not sure if you did pan the instruments, but to me it sounded like it needs some work.
Remember, at least change the dynamics! If you write the midi files in guitar pro, there's a tool that actually does the dynamics through the whole song for you!