Freddie Mercury
Simply because of the wide range of music he could write, sing and play.
From gorgeous piano harmonies to all out head banging rock, and he made it all look so simple.
A rare talent indeed.
First off great example, but it has me rethinking the notion of Bob Marley. I still believe is/was a musical genius, but he did not do it alone. Freddie, like John & Paul (and George), Sting, Townshend, Brian Wilson, Miles, Chris Thile, Zappa, Marley, Basie, Ellington, Django, and others, isn't creating in a vacuum or alone. Even when some of these folks brought in a tune, it was the collaborative effort, the input from band mates and the collective interplay and arrangement that took the work to another level. Often the solo work from these artists can be found to be missing something or less than (or even garbage) compared to the work they did within a band. Freddie's solo stuff wasn't that great, Paul's had highs and lows (and really lows), Bob rarely worked without the Wailers (and they had a huge had in shaping the sound and feel of his music). Pete sure as hell wasn't telling Keith or John what to play or how, Zappa was notorious, like similar leaders, for nabbing ideas from his backing bands' jams or improvs and turning them into songs without giving them credit. Prince, Miles, the Rolling Stones, and others have been guilty, accused, or rumored to do this as well.
In short, genius can be a group thing just as easily as it can be rooted in one brilliant mind. Even Peter Gabriel corralled a core group of musicians to execute his ideas and contribute their own...folks he could, did, and does count/trust on to play the right part without prompting while also being able to work with others and adapt as things morph into something else. Obviously Gabriel is not the only artist to do this.
I find the music I most enjoy is collaboratively created. The interplay between two or more musicians is where the magic really happens, be it the creative process or in performance.