Since when is being "average" inherently bad? If you are "superior", then people are going to expect more from you and possibly over-estimate your abilities. You're also going to be expected to be responsible for your "gifts".
U.S. culture emphasizes the importance of exceeding intelligence, wealth, and prosperity. Circumstantially, these things aren't bad either, but they're definitely overrated. So overrated, in fact, that they force many of us to underrate our common selves.
Also, your insecurity maybe a byproduct of inadequacy, but it may also be a cause of subsequent insecurity or more insecurity. ie. vicious cycle.
Many people go through this phase of realizing that we can't be all of what we dreamed of as children. We may blame our parents for supposedly deluding us into thinking we can accomplish all things. From what you've said, it doesn't sound like you had dogmatic parents who coaxed you into being who they wanted you to be. It sounds more like they were willing to facilitate your progress in whichever way you desired. The trappings of multiple choice have now left you waning, but I don't think you're incapable.