I think many people have touched on alot of great traits. Being creative in your beat making, from my experience, represents a portion of the equation. Realize that as a great producer, you are part of the creative process beyond the beat. I have always taught artists to consider their relationship with the producer to be analogous to that of the members of a construction team erecting a building. They both bring something integral to the construction of the song. I think there are many talented beat makers. To be a great producer, you need to be an active member of the process cradle to grave.