Elvis Presley was and still is over-rated just like Britney
Spears is. Okay, how many of Elvis songs do they still play on the
radio these days? He did not write many of his popular songs. He was a mediocre guitarist and toward the end of his life in his
late 30s he got too fat to shake his bom bom thus defying his Elvis the
Pelvis persona. The actual King of Rock N' Roll  as many contend was a pioneer called Chuck Berry back
then but he was too black to be dubbed so. The second close to Berry was
probably Jerry Lee Lewis. One of the theories behind Elvis garnering so much media attention was because of his appealing White and Jewish background.

Regarding Obama Vs Michael Jackson, Obama was a glimmer of hope of the time for the voters after the
Iraq War Fiasco, Global financial collapse engineered by the Republican
economic philosophy which went disarray after so much excess. Obama's orating skills,
stances on certain issues, brilliant campaign strategy and likable personality
are some qualities that set him apart from his contenders and also helped in raising a lot of money for his campaign. He is barely
been in office for six months and has a lot to prove. God forbid but if
he died suddenly while in office, the news of the death of a sitting American
President would definitely send shock-waves across the world. But if it
happens as it should that is well after him leaving office, it will be as normal as death of Reagan who was a wildly popular President too.
Still many years from now , I bet you would get stirred up with Michael Jackson's song suddenly appearing on your radio and you would start dancing with your torso on your car-seat
as opposed to Obama or Reagan speech being played.

Regarding Pele and Maradona, they are definitely icons but only to
people who follow soccer as being most popular game in any country.
Unfortunately, some of the most populous nations just to name one or two
like India and USA are rather more obsessed with Cricket, Baseball or
American Football.