you have a long buildup... I really don't mind it - the bass line has a simple entrancing effect. but you gotta explore the theme a bit once you do finally build up. You can try weaving it into the boss theme and then weaving back, see if the themes work together as countermelodies, try a new or modified melody on new the bass / rhythm, do an a/b section thing, etc.
The guitar sounds fake and mechanical - try to work on the timings and the velocities to give it a more human sound.. and probably find a new sample. Ideally, you'd want to find someone to play it for you. Things also get pretty muddy with the reverb. Maybe try playing the melody an octave higher (sounds like it should be within the range of the guitar) to give it some space in the mix, though this would probably be fixed by working on the reverb, humanization and stuff.
I forgot how much I enjoyed this piece from Zelda II.