What would you rank as the ,'Best Back Exercise', ahead of the ,'Pull up'?
Best for what purpose?
Best for static strength of the upper back and spinal muscles? Probably the deadlift.
Best mass builder for the upper back? Probably the chest supported row (aka "bench row") - though any full range of motion row that readily lends itself to the full complement of bodybuilding training strategies (heavy, light, drop sets, pyramids, etc.) can be just as good.
Best for vertical pulling strength? Weighted pull-ups or pulldowns - pick your poison.
Best for athletic power? Power cleans, since they improve your ability to transfer hip and leg power through your back and arms.
Its all about the best tool for the specific goal.