Let's ask the question at the end of Messi's career. At this point, he is 24, has only had three injury free years (though all have come these past three seasons, so maybe he's just finally growing into his still small frame), and while WCs shouldn't be a factor in debates about individual skill, if you are talking "greatness", well, winning matters. If Messi's career arc progresses as it should, though, in 10 years I would be willing to have this discussion.
Messi in contrast plays in one of the most talented side in the history of the game. Messi might be the catalyst behind the triumphs of Barca in recent times, but he was well assisted by a huge number of exceptional talents.
Messi is actually 25 years old. Maradona won with Argentina in Mexico 86 with 26 years old, and until Mexico 86 he failed in Barcelona or with Argentina in Spain 82. We only can compare them when Messi is retired, but Messi with 24 years old have won many more titles in Barcelona, than Maradona in Argentinos,Boca, Barcelona, Napoli, Sevilla.
Messi is a great talent who does not come every decade, However, ot's NOT about the age ... as Pele won WC at only 17, Ronaldo led the team to WC final at 21 ... all were younger than Messi now. It's a question how Messi could overcome obstacles and reach the goal by his talent ... Notice that Napoli , Argentinos, Boca ... were far from this Barca quality
[I give the "nod" to "M10" and I can't STAND him on a personal level. He was definitely one HELL of a footballer, though...]