In order to be the world's tallest man you need to be officially measured. So there's one guy who's probably the world's tallest man, at 8' 5". But he refused to be measured.
That leaves the second tallest man as the world's tallest man, at 8' 1", a guy from China.
The previous world's tallest man, until the second tallest man became the world's tallest man, was 7' 9".