Intelligence I think there are different aspects to intelligence, and I think intelligence also has a strong psychological aspect. IQ tests, for instance, tend to measure more of a reasoning ability. There's not any questions, for instance, on how to act morally in certain situations, there are no questions that involve creativity or intuition (mental powers essential to making any kind of art, for instance). How would you make a test that measured creativity, anyway? The problem with trying to measure intelligence at all is that some functions of the human mind don't avail themselves to quantitative measurement. Really, the potential for human intelligence is far-ranging; consider savants, for instance. There's also an aspect of intelligence called common sense which many of the "masses" possess, and many of the intellectual class do not.
The other aspect I mentioned is the psychological aspect. Our own perception of our own intelligence tends to be a self-fulfilling prophecy; if I consider myself bad with logic (which I do), I'll probably continue to not really try to learn it (formal logic anyway), unless I really push myself outside of the bounds of that psychological belief about myself. Of course, that belief is based on experience. But, we create a picture in our minds of our own intelligence, and we tend not to try to alter that picture. In-grained beliefs about ourselves are hard to change. The other day I was covering a shift at my old job, and the new kid, a post-grad, hasn't learned how to close out the shop after working there for a year. I walked him through the process, and I could tell he was intimidated that I knew how after not having worked there for over a year, and I could tell that anytime I explained an aspect of the process, he ingested that not as useful info for future shifts, but as yet another voice telling him "you're dumb, you can't learn this basic shit". I could tell all of that, so I tried to be very positive about how I explained it, but that didn't matter. He believes he can't learn it. But he can, if he would only change his beliefs about his own intelligence. He's very good at all the other aspects of the job.
So all of that in mind, as far as trying to measure other people's intelligence, and figure out whether or not someone is intelligent, I don't even think it's worth spending much thought on. There are different sorts of intelligence. It seems to me that what we often define as intelligence is just the ability to reason clearly, or do tasks that involve complex processes. If you see the human mind as having a myriad of modes, of ways of thinking, then intelligence becomes a broader spectrum. Someone unable to reason clearly may be a brilliant artist. Someone who can't even carry a tune may be a brilliant scientist. Someone with a gift for writing may not have a gift for oratory or conversation. What's the point of even trying to figure out "who's smarter?"