That is a misconception that even Einstein fought his entire life. It was largely based on a misreported story by the New York Times. Arthur Eddington, the British physicist who attempted to use the eclipse of 1919 to verify General Relativity, took advantage of this misconception. According to Eddington, after he presented his results to the Royal Society a member of audience approached him, saying, "I understand that there are only three people in the entire world who understand this relativity business." Eddington stood speechless for a moment, and his inquistor insisted, "Now, don't be so modest, man!" Eddington snapped out of reverie and replied, "No, I'm just trying to think of who the third one might be!"
Eddington retold that tale at high tea in Oxford for decades.
Einstein's son, who became a professor of civil engineering at Caltech, insisted that his father's distinguishing trait (a lot like Richard Feymann) was his absolute refusal to take anyone's word for anything. He would not accept something until he had thought it through for himself.
Too bad American voters aren't like that.
Which probably explains why he didn't do all that well in school. Unlike most famous people in math and science, Einstein didn't have a famous adviser. He didn't get along with the advisers he did have and dumped one of them. He was pretty much self taught, and one of a kind.
While some may have a general IQ equal to or greater than Einstein's, I doubt anyone has ever equaled his ability to convert the real world into geometry in his mind.