Hi William,
As you said, it's extremely difficult to pick one melody out of the lot. It would always be a very personal and subjective choice. I my case, I've written in so many different styles, instrumentations, with our without choir, for solo voices, orchestral tunes, themes of all sorts and purposes, religious, musical stage play... In Dutch we say: "It's like comparing lemons with apples". But I like the idea to come forward with one preferred melody or tune or theme (whatever you have meant).
This one could in some way be representative (from about 4:32 to 5:40). The rest is mainly a fully orchestrated Czech folk song for choir and orchestra.