Absolutely not.

An accurate IQ test requires several sessions of one on one time with a qualified psychologist, or at the bare minimum a well administered standardized IQ test. Most former presidents predate the existence of IQ tests and I don't think that the presidents that could have taken one ever had their results released to the public.

These lists are there for fun and shouldn't be taken too seriously.

Well, there are a few things you'll have to keep in mind. Alfred Binet created the first IQ test in the early 1900's. His test wasn't designed to show how gifted a person was, however. The IQ test was only meant to gauge the disability of "retarded" children and persons. In 1916, Lewis Terman at Stanford college revised the test and created the Stanford-Binet IQ test that is used today. This means that anyone who lived before 1916 could never have taken an IQ test. If someone tries to tell you that George Washington had an IQ of 150, for example, there would be no way to prove this.

I've seen reports of President Kennedy having an IQ anywhere from 118 to 174. I've found no evidence that Kennedy ever actually took an IQ test which means that this is all just guesswork.

Now, estimating the IQ's of historical figures is extremely difficult. For one, the Psychological community still doesn't agree on what exactly "Intelligence" even is. Most IQ tests only test "book smarts" which we've come to realize isn't everything in regards to intelligence. A relatively new theory by Gardner says there are 8 types of intelligence: Musical, Bodily, Visual, Verbal, Interpersonal, Intrapersonal, Nature, and Logical.

So basically, It would be impossible to figure out the IQ of Genghis Khan when we can't test him AND we don't even know what intelligence is. It's all guesswork.

The entire idea of intelligence testing is a controversial and flawed one. Stephen Jay Gould's The Mismeasure of Man should be essential reading for, well, everyone.

Related question. I know senior Nazi officials and German military leaders were given IQ tests following World War 2. Was there any conclusions drawn from this study?

So is this study not accurate? It's from an academic journal and while I have not read it all, it does seem to estimate the IQs or intelligence of presidents.