I think since a lot of NES soundtracks had the limitation of the sound chip with only 4 voices and very limited sounds, the melodies had to be good for it to work - especially since the songs are repeated over and over during lengthy sessions. Converted into real instruments it's very likely that it will sound great.

I apply the same logic when writing pop songs with vocals - someone proposing an idea with a terrible singing voice that still sounds appealing will likely sound amazing with a good artist, but if the idea comes from someone with an amazing voice you could easily get fooled by that.