I think IQ tests and other measures of intelligence are measures of what I would call second order intelligence.
If you take an IQ test and introspect about the thoughts and processes running through your conscious mind, you see that all you are doing is manipulating imaginary objects. Translating, rotating, flipping, summing, superimposing, labeling objects with other objects, be it sounds, images, feelings, so that you may hold and then recall more effectively.
A computer works quite the same. At the foundation everything is a number in binary form and everything that happens is an arithmetic operation. through layers of abstraction it is possible to turn that into hubpages and the text on the screen.
When you introspect you see that your intelligence is quite primitive. The operations taking place as you think and problem solve are simple and very much tied to your senses and your model of the physical world. When we ponder over highly abstract concepts you see that you're really pondering over real objects that you've acquired through your senses. And even then the abstraction level is what I called second order, compared to a computer system which may go through many layers upon layers of abstraction.
So it would seem to me that intelligence is a measure of the speed, error rate and bandwidth of your brain and and then the abstract as measured by an IQ test.
Then there is emotional intelligence, since we cannot separate our activities from emotion this is obviously just as important. Your ability to handle pressure, to understand yourself and others, is paramount to being effective in the world.
Anyway, an IQ of 160 and above is high enough, far enough away from a standard deviation of 15, that it is certified genius.
One difference I would note of people I've read about and seen on TV with IQs in the 200s in some cases is that they are remarkably practicle, normal, human, and have enormous memories, probably a consequence of interconnected of ideas.
The only difference I see is that they are much more at home in the realm of the abstract. It's as natural to them as a bouncing ball is to a monkey.