I don't "think" I'm of more than average intelligence, I "Know" it, I figure things out almost instantly, when others around me take for fucking ever, I retain what I learn and use it creatively with ease, and when it comes to adaptiveness to situational variables and conversational subject matter, I'm a fucking social cameleon, which makes me wonderful as a salesperson, as I overload people with positive facts about what I want to sell people based on my judgement of a person through small talk before I try my pitch.
I'm not the best when it comes to grammar on forums, I will admit.
And no I don't think I'm a supergenius, just I've seen way way too much evidence in my life to suggest I'm a cut above most people when it comes to creativity, problem solving, pattern recognition, and situational analysis(usually for the purpose of avoiding hazards, and maximizing my proffit/loss ratio).
Also I find average people extremely annoying, and they always ask me for my opinion or try to get me to fix their stuff all the time, or like teach them stuff... I help who I want to help, and usually the people I help are the people I'm already friends with, and the only reason they need help most of the time is because they need a few extra hands for moving furnature or basic things that ANYONE who doesn't have robo minions or the like will need a bit of help with, after all moving a piano is not generally easy for one person, especially if you don't want to damage it or anything else in the process.
Also to be fair about this poll, you're asking an online community, more specifically the escapist community, the poll only accounts for a tiny portion of people of which all of them can obviously use a computer, and comprehend complex concepts to some extent, such as the internet...
If the polls read more people thinking themselves less than average, I would be deeply troubled at the state of this world.