Whoever Germany replaces her with would almost certainly be a better version of Merkel, because the only way to replace her is an SPD-Linke-Green coalition, which would put forward someone who simultaneously backs away from the hardline austerity tearing Europe apart and the anti-Russian hysteria of the Atlanticist Right (thanks to Linke).
The most likely replacement for Merkel is within her party, when she chooses to retire. But, even if her replacement were due to the left-wing parties winning an election, that is no guarantee of continued German internationalist leadership. If Gerhard Schroder were the German Chancellor today, no one would be calling him leader of the free world.