It doesn't matter if he wins it on his own (ala Maradonna) or not, he has the abilty to do it imo.
It's a competition that comes around once every four years, and if you win it puts you in to a very special class of players.
It's not like any other competition in the World, no domestic cup comes close. (yes that includes the European Champions League, sorry Sky syndrome people)
Argentina have the quailty of players to win a World Cup, infact I still rate them capable of winning the one this summer. (forget all the "not playing well ****" same was said about Brasil and has being said before, the World Cup does funny things to teams)
Messi isn't Best, Best was never going to do much on an international side because of whom he played for (no disrespect), Messi is part of an amazing footballing nation who produce great teams.