Nothing to do with 'character'. It's about achievements on the pitch. Maradona performed miracles with teams of ordinary players around him. Messi's achievements have been in teams full of superstars.
Messi performs miracles far more often than Maradonna did, his teammates certainly contributed to that however that doesn't change the fact that for a few years he was routinely performing at a level that Maradonna achieved only rarely even when at Barca.