I'm not drawing an analogy between language and music directly here;
but have you noticed that the best melodies, the most satisfying ones, almost seem to "talk?" They have rhythmic patterns which move in a surprising and satisfying way and land in places which "rhyme" as it were, like poetry. This may seem like a trivial post, but...its pretty easy to find examples of pieces with melodies that just kind of meander around, and other examples where the melody has this wonderfully....tangible quality to it. Some might say this has to do with a strong harmonic progression, but then sitar music, which arguably has no real harmonic movement at all, often has this quality I'm talking about, though in a different manner than Western music.