If we're talking about power as influence over the maximum number of lives, I'd say we don't know the name of the most powerful person in the world. Probably never will.
But he or she is definitely out there. And there probably is a person that runs it all behind the scenes style.
May seem too conspiracy-esque, but I believe it.
I've always thought of it that way, not just one person but a small group. Kinda like the people who run Area 51, I heard somewhere that if the president asked to enter certain sectors then he would be shot. There's no way that the president, for example, runs everything in the country and there is also a lot he is unaware of. You really think that the greatest minds in the country came together to run the country and said to each other "Maybe the people in this panel should be voted in"? I think not. They probably discussed it and thought, "We can make the public happy by making them THINK that they elected their ruler and they are so stupid and so influenced by the media that they'll believe it".
They are your leaders. They are the people who control everything. The media, everything. When you consider it, it isn't such a stupid idea. The leader of a country has to make hard decisions, like whether to go to war, or WHETHER TO DESTROY HIS OWN COUNTRIES WORLD TRADE CENTERS, for example
If the president had to make a very tough decision like, for example, to bomb a town containing a group of terrorists, and the public found out, he would be voted out of office ASAP. This panel of people can make the toughest decisions without fear of being voted out of office. Ever notice how during the lead up to an election a leader will make decisions that serve no other purpose other than to get him voted in for another term (in Australia, anyway).
Well that's what I think about who really runs the country. Those people, obviously, are the most powerful people in the world.
Also, the President of the US wouldn't be as powerful as you might think. He doesn't single-handedly run the country, and he is voted in by people whose lives revolve around the media. If anything, he is the best marketer alive