The thing I most appreciate, when it comes to music, is a powerful, dominating singing voice. I respect a song's melody and the work of great musicians, but it's that natural power I love the most. First off, I'm a huge Queen™ fan, so my opinion is biased. Even with that said, I think it would be hard to argue against the super-human singing voice of Freddie Mercury. Above is an article about the science behind his amazing singing ability. If you have never listened to Queen™, but have an appreciation for truly amazing talent, take a listen, the man was amazing and a huge loss.