Who is the most popular human being on earth? Interesting question.
Let's rule out any Hollywood actor: their popularity is very limited (to the developed world)... and there's way too many of them, so different people have different favorites.
Let's rule out anyone in the west, actually. There' s way too less people in the western world. If the question were "Which person's popularity can be transalated into the most money due to ticket sales and endorsements?", then perhaps western celebs would stand a chance. But not as things are right now.
So, of course, the possibilities are essentially either Chinese or Indian celebs ... with billion plus people. I have a gut feeling that the most popular person in the world is Sachin Tendulkar. I will make my case in the following paragraphs.
What do a billion people have in common in India? They do not have a common culture: the culture of the North-east differs from the south, the culture of the east and the west is different. Hinduism? There are more variations within Hinduism in India than there are between different religions at other places!
Democracy? Yes indeed; but the people of the North have never heard of Karunanidhi, the people of the west have never heard of Budhadeb Bhattacharya. Hindi Films? The big B might have more than a 300 million loyal fans (more than the productive population of the USA) but the average Apparao down south would have a tough time placing him.
Cricket is the only thing that unites India's diversity. India's massive talent pool of cricket is (often cruelly) refined and refined again into an elite squad: the men in Blue. And Sachin Tendulkar is the formost and the bluest of them all. A man who's antics on the field make many an Indian's heart beat faster. A person who drives bowlers to utter disarray on his day. A humble genius.
For he carries the hopes and aspirations of 1 billion people. He is among the few things that the people of this entire mass of people actually hold close to their heart.
And part of the problem is that. There's enough talent in India to produce 20 Sachin Tendulkar. If we search deep enough we will find a fast bowler that will put Shohaib Akthar to shame. A spinner who will spin 180 degrees! So, all the people of India look at Sachin - perhaps because they have no one else to look up to.
I'm not too sure about China, but I'm sure you see that Sachin has a strong case to be crowned "most popular man on earth".