Genre Island is an interesting concept, although as was said, when it came time to do rankings, I don't know how well it would work. If someone makes a jazz playlist and a listener just doesn't like that genre, it won't do well on their rankings.
Unless we put restrictions on the type of voting this time, like if each person had to vote for songs, presentation, etc.
Just thinking as I'm typing here. You could have each person vote for a playlist based on the following:
33.3% - Songs
33.3% - Sequencing, transitions, flow, etc.
33.3% - Representation of genre (or something along those lines)
People could rate each part on a scale of 1-10, and the average of all three would be the final score. Then you submit your rankings based on who has the best average score, from 1st to last.
Could work possibly.