#2 Gave his best, took them to their best
Argentina have no silverware to show since 1993. In the period between 1994 and 2006, they barely made it to one Copa America final (2004) and two low-key FIFA Confederation cup finals (1995, 2005). Leo has taken them to four finals between 2007 and 2016.
Even in the two World Cups, he played a decisive role (2010 and 2014), he took them to quarter finals and finals respectively. In the previous four World cups, Argentina have at max reached the quarter-finals (1998, 2006).
So really, Messi has taken them to an optimal point, up to where he could. I dare say, where Argentina could at max achieve. They had an above average team, but never a world-beating one.
To add, no non-European team has won a World Cup held in Europe since Brazil in 1958. In cooler Russian conditions, the chances of Argentina winning World Cup 2018, are very very remote. It’s better to retire being remembered as one who took the team to three consecutive finals.