I think this is a riddle for almost everybody. The list of known genres/styles is huge:
(still more are listed in numerous music libraries), and there are no comprehensive definitions of them. One can only judge as follows: "X writes in style S. Y is similar to X. So Y writes in style S", which is hardly a correct reasoning. Songwriting competitions usually announce some 10 genres, e.g., "Country, Folk, Adult Contemporary, Dance, Christian, Hip-Hop, Rock, Lyric Only, Instrumental, Pop", many of which intersect with each other, so even for those participating in a competition it is hard to decide to which category his music belongs. In classical music the situation is simpler: genres are correlated with music form, tempo and instrumentation.
Do you think it is possible to apply some similar reasoning for arranging what we write and hear today by music genres?