The music I listen to usually includes complicated melodies, lots of different instruments (most of which are difficult to play) and very fast playing. I'm not really sure what makes any given instrument more 'musical' than another, but I believe what I listen to is more music than rap or pop because the lyrics and vocals always play backseat to the music, which is generally the opposite in rap and pop.
Another thing I like about in my music is the types of instruments they use. I mostly listen to metal with keyboards or other classical instruments; very few bands I like have only guitars, drums and a base. And just the fact that these guys can play everything so fast and get it all perfect is another reason I consider it music and not just noise.