He's obviously marvelous, but I can understand people who find him a little bloodless. He quietly goes about his devastating brilliance, but some possibly prefer the emotional overload of Maradona. Messi is self-contained. He lacks the drama of a Ronaldo. Technically, I don't think I've seen anyone better than Messi. But as a force of nature, Maradona gets my vote. But you can't really compare eras. Maradona played in an era where the great players were brutalised and assaulted from behind. The 1986 World Cup had all four of the best players in the world - Zico, Rummenigge, Maradona and Platini entering the tournament with varieties of injury. They were crucified by Gentile, Goicoechea, Camacho and the like, notorious hatchetmen who fouled with impunity. Messi and Ronaldo had almost injury-free careers. That was only possible thanks to rule changes and clampdowns.
Also, the offside law changes over the years opened up the playing area for creative players. In the 1980s, Serie A was characterised by multiple 0-0s and 1-0s every week as space, and goals, were at a premium. It was a different game then. Messi is, for me, the undoubted greatest player of his era. Beyond that, it's apples and oranges.