Man, I could write forever on this subject... I'll try and keep it short as I can:
I like to think I'm bright, we all do. Am I above average? My I.Q. test says so, but what does that mean in real terms? I don't have the first clue how to figure out what's wrong with my car - is my mechanic brighter than me? If I were to get into legal trouble, I sure wouldn't represent myself in court, but does that make my lawyer brighter? No, but their areas of expertise are different. Could either of them sit down in front of a computer and make it do anywhere near what I can? It's doubtful. But that doesn't necessarily make me smarter than them either.
So what's my point? What makes a programmer a "rockstar" as someone else put it? They know the API of their entire language inside out and can code it blindfolded with one hand tied behind their back. Are there such programmers, I imagine there are some, but I doubt there are very many.
(Scenario) You've come across such a rockstar and you're thinking about snapping them up for your team. Their overall attitude has a few awkward edges, they're somewhat arrogant and make a fleeting comment on "lesser" programmers in the interview. They get 100% on your interview exam in record time and in ways you'd never dreamed you'd see it done in 20% less code than you've ever seen before. Their references are excellent, but all their experience has been in an academic environment, all their projects have been in scientific sanitized environments and they've never had to deal with end users, think on their feet or code to extreme scenarios caused by unconceived idiocy by some computer illiterate end users. It's not hard to see that this rockstar programmer could quickly fall to pieces on your team. So are they really the rockstar they seem on paper?
Most of us are average in many areas and we excel beyond comprehension in others. So this measure is extremely subjective. I excel at writing data management applications to be used in intranet environments where users are unlikely to be extremely (or even partially) computer literate, but if you wanted me to write a computer game that hosted complex artificial intelligence and graphics, I wouldn't have the first clue where to start beyond my good friend Google...I'm sure I'd eventually figure it out but not before being booted out on my behind for incompetence. However, a friend of mine that's never professionally programmed in his life can run circles around me when it comes to that stuff - and I've been programming professionally for 12 years.
Do I consider myself a rockstar? Of course I brag to my colleagues and future employers that I'm a rockstar and I complain to my wife about all the idiotic things I come across in a day, we all do. Inside though, I know there's always more to learn and while I might consider myself a rockstar in my niche, if someone decided they needed that game written, I'd consider myself beyond incompetent.
It's not what knowledge we have, but how we attain more knowledge and how we apply that knowledge that makes us stand out in the crowd.