OK. Great first piece! I think the hardest thing in the world is to write a really good melody, and the best way to write one is to write lots and lots until you get one that you love.
A few thoughts: your tune depends on arpeggios, primarily of G major, for much of the time. When not arpeggiating, it is usually moving in scalar motion (by step). Both scale and arpeggio are crucial but somewhat non-descript. A really good melody will find a mystically perfect balance of steps and skips. Also think vocally: the high notes should feel like you are reaching for them, as in Inisheer or South Wind.
The other main thing is rhythm. I think rhythm is actually more important to a good melody than are the intervals. Again, balance is the key: not too regular, but not too weirdly syncopated. As we look at our favorite tunes we find this perfect balance.
So write more, and share it with the Chiff People!
