Messi deserved the Golden Ball. He was the star for their team. Nobody in the tournament was guarded like him, yet he still scored 4 times and got his team to the finals. Teams always had 2 or 3 and sometimes 4 defenders constantly around him. He made lots of great pass plays when surrounded, only to have his team mates, time after time, mess them up. He did have his shot for legendary greatness in the final game against Germany, but just missed the goal.
Argentina really missed Di Maria in the finals(and in the previous game). Their front line and midfield players looked very tired as well. Hopefully, FIFA has both semi-final games on the same day in the next world cup, so 1 team doesn't get an extra day of rest.
Robben was probably the 2nd best player in the tournament. He would have won the Golden Ball if they had beat Argentina. Just like Messi, Robben was critical in almost every match for the Netherlands.
But considering all players of the world cup, Messi wasn't even close to deserving it. It was just a consolation because clearly a few from Germany deserved it more.