This question has a simple answer.
That's definitely not the end of the discussion though. I think we need to play a little devil's advocate here.
Lionel Messi is one of my favorite players, and how can he not be? Every time he touches the ball you never know what he's going to do. He's one of the most creative guys in the game, but he is not all flash like some. He puts the ball in the back of the net, and he does it a lot.
One critique could be the quality of his team. Barcelona have been dominant over the past few years, and Messi is a big part of that. But would Messi be as good if he didn't have the supporting cast he does?
Last year Messi took home the Ballon d'Or (European Footballer of the Year) and FIFA's Footballer of the Year award.
Two of Messi's teammates, Xavi and Andres Iniesta, were on the shortlist of 10 players to win the Ballon d'Or award. Both players are midfielders, and both deserved to be amongst the top 10.
Diego Maradona carried Napoli on his back and led them to two Scudetti (Italian League Championships). You could say his Argentina team was strong, as they won the World Cup in 1978 without him, but he was pivotal in Argentina's triumph in 1986.
Pele, at the age of 17, helped Brazil win the World Cup in 1958, and he went on to lead them to two more in 1962 and 1970.
Does this mean we need to see Messi lead a talented, but at times complacent, Argentina team deep into the 2010 FIFA World Cup?
To an extent.
Argentina is really stacked with forwards and some good midfielders but they do lack in the defensive department. This could be their Achilles heel, but it wouldn't have anything to do with Messi. But the best of the best find ways to make their team win.
There is no doubt that if Argentina finds themselves winners of the 2010 World Cup that Messi will be player of the tournament.
Maradona managing the squad is a problem though. He really isn't that great of a manager and Argentina did poorly in qualifying, finishing behind Brazil, Chile, and Paraguay.
If a 22-year-old (23 after June 24) Messi can take a nation on his back and lead them to the promised land, that should solidify him as one of the world's greatest. But the fact that he is only 22 can work against him.
Ronaldinho won FIFA's World Player of the Year when he was 24 and 25 years old in 2004 and 2005 respectively. Since then his play declined and Barcelona eventually sold their once prized asset to AC Milan.
His play got worse. Some credited this to his newfound love of the "night life." A tendency to stay out all night and party.
It didn't help that Kaka was playing in his position.
Now that Kaka is gone, his play has risen, but he isn't even near his glory days.
Some people may not want to hear this, and some will take it as a stereotype, but a lot of South American footballers find it too much when they move to Europe and get those big contracts. They let it get to their heads and they get a little homesick (see Robinho).
They start partying more and their work ethics start to decline—along with their play.
I doubt Messi will run into these problems, but it's been brought up that maybe he has maxed out, and that the term "nowhere to go but up" doesn't apply.
I disagree with that notion, but will recognize the slim possibility that Messi has reached his full potential already at such a young age.
Messi will be under a microscope this June. If he is able to deliver a World Cup trophy to Argentina, he will be able to be put in the same sentence as Pele, Maradona, Platini, Beckenbauer, etc.