I think we should start with the definition of "average." Average is the rule. The majority. Average does not exist without a group where a pattern of common characteristics can emerge. When looking outward, we can easily identify who is average in the context of the group. However, we all live as individuals. When self evaluating, and looking inward, we see only our own differences and traits and often lack a true sense of the group. From there, I'd wager most of the time your answer depends on your level of self esteem instead of true self-awareness. 

Average is also synonymous with normal. As contradictory as it may seem, a part of being normal or average is being unique from other humans. Taking this simple fact into account, it is safe to assume that most of us are above average in some facet of our lives.