I love chess.
I was thinking about this question today. I wonder if one tends to find people to be smart if 1) a person is good at something one values themself, or 2) a person is good at something one is poor at themself.
I tend to find myself thinking people who remember names, dates, details to be "smart" — and that happens to be something I am incredibly poor at. Coincidence?
But that's not to say that people with good memories aren't smart.
There are people with great memories, people who are whizzes at math, people who excel at engineering, spelling, writing, singing, playing an instrument, painting, learning languages, solving problems, athletics, nature, biology, teaching, making connections between complex ideas, and creating.
Western culture tends to value people strong in maths and writing.
And I don't know about genius smart, but as a general rule, we tend to find people with excellent self-regulation to be "smart."
So I guess there has to be somebody alive who is the most talented human in all the above areas. Would they be the smartest person I know if I knew them?
Also, I've always made a distinction between smart and wisdom. I define wisdom as the ability to make good decisions. Someone could technically be very intelligent but not wise. At all.
So who is the smartest person I know? It's probably a toss up between a buddy of mine who is a biologist who seems to know a lot about a lot of subjects (although he is not intellectual in the least) and my wife who has an impeccable memory (which she gave to our daughter, whose is even sharper) and an incredible ability to consume and process information (and who also is not intellectual).