Noted, but not the point i was making. Leaders can stay in power for an extended time and be effective and not corrupt.
That depends on what you call "stay in power".
Being a Chancellor is just that: she's the head of the German government. She is not head of the State (the country). That's Frank-Walter Steinmeier. He's the Bundespräsident. Another difference is that there are multiple parties in the German Parliament. Those parties have to form a coalition to get a majority to form a government. E.g. the current German government is a combination of three parties (CDU, CSU and SPD). As you can see, Merkel has to share power with a lot of people.
This is not like the US, where you have a "winner takes all" mentality. You chose one winner, and he determines everything for the next 4 years. I think that sucks. (E.g. the way the electoral votes work per state). And you give power to a single person. (Luckily you have a separation of parliament and government).
Also, Merkel is a very special person. I do not agree with her personal views (fuck Christianity). But she is a honest person, I think. Coming from the ex-DDR. Having been a real scientist. You won't find more people like her easily.