There are many different prisms through which success can be evaluated in so many different aspects of football. With the continued advancement of analytics, in fact, there seems to be no shortage of tools at our disposal on which to judge performances.
One statistic that I like, even if it introduces a degree of subjectivity into the discussion, is the notion of a catchable target, which basically helps the process of not penalizing quarterbacks for mistakes that his targets make. A quarterback can make a great through on a pass attempt that was not completed, and that should be acknowledged.