Tendulkar, by volume. He would have got brutal majority vote of a 1.2bn population.
In terms of world wide popularity, I think it'll be Maradona - because of the game he played.
If I bring popular players within the countries their game is popular (& not considering the population mass), probably the most popular player will be Federar, while most respected Ali. But, players like Ali, Federar, Jordan, Woods, O'Sullivan, Schumi are unique in their sports.
If I go by individual peak compared to contemporary generation, I think Brandman has to be at top in terms of stats while Imran for few years probably reached the highest individual peak of contribution in a team game. Then comes Jordan (though I think, Labron has surpassed him)
In individual game, I think the Md. Ali of Huston Astrodome at 24 (against Ernie Terrell & Cleveland Williams) was undoubtedly the best ever - don't think in any generation, any weight class, ever any boxer could match him. In a niche sports, but Ali's superiority in brilliance is probably matched only by Jahangir Khan & Ronnie O'Sullivan - on his day, Ronnie is twice the entertainer than the next 2 men, who has 11 World titles among them (Davis & Higgins). Then comes Woods & Federar.
I don't rate Schumi, Fangio or Agostini that high, because part of their success is the machine they drove or ride.
Sadly, no footballer comes in this list, because in a team game none of them carried their team like few other sports I mentioned. Pele had at least 5/6 ATG's in each of his 3 WC winning team, same can be said for Zizu or fat Ronaldo, while Messi is a looser outside Barca & Cruiff or De Stefano or CR plays for weak national teams. In that regard, I'll put Maradona at top, for his solo show of 1986 - I am sure, even die hard Arges fans won't be able to name 6 other team members of his 1986 & 1990 team - Pele had half a dozen among Didi, Vava, Zagalo, Zito, Santos brothers, Amarildo, Garincha, Jairzinho, Garson, Tostao, Rivelino, Carlos Albarto around him in those 3 WCs.
