It's difficult to compare Maradonna and Messi, one was a flawed genius, the other a consummate professional.
Maradonna single handedly won his country the World Cup in 1986 and Napoli's first Serie A title 1987, with his brilliance pretty much condensed in that two year period. His wild lifestyle, involvement with unsavoury people and being quite partial to the old Columbian marching powder led his career downwards from there on. Internationally Maradonna leaves Messi behind, but that's not the whole picture.
Messi has at domestic level has an unrivalled record, he is a one club man and has delivered every season. It is debatable whether Barcelona would have had the same success without his contribution, which for me makes him the better all round player in terms of achievement and professionalism.