I think it goes far deeper than winning a World Cup. Maradona came from the slums of Argentina like so many of the great South American stars, and he went on to be the best player in the Argentina league while he was still in his teens - he was an idol within Argentina well before his national exploits. He considered Boca, the biggest team in Argentina, his spiritual home and had an instant connection, a real love for the club and what it represented. It's the same at Napoli where he's idolised for far more than his contributions on the pitch. He identified with the Neapolitans, he saw it as a great injustice that Southern Italians were treated as second class citizens and fought relentlessly to bring some prestige to that part of the country.
It's the fact that Maradona's values - namely that of fighting for the underdog, completely disregarding any notions of social class and treating people as equals regardless of their wealth or stature - correspond with the values of the majority of Argentines that elevated him to godly status. Messi doesn't have any of that. He plays for the most attractive club in the world, has an easy life now and had a relatively easy upbringing back home and in a lot of ways is Spanish in nature that stop people loving Messi. His performances for the national side will get people on his side but he'll compete with Maradona's god-like status IMO because he's a fundamentally different person. He doesn't have character in the way El Diego does.
Messi and (early years) Pele are awfully similar in a lot of ways, personality-wise. They're both just Mr Perfect, too nice and too simple. That's why even though Pele is revered in Brazil you still have people saying that Garrincha's #1 - it has nothing to do with who the better player was, it's entirely about their character and how the fans identified with them. I don't see that ever changing with Messi. He's not interested in that kind of adulation, he'll just let things be.