That will always be a matter of opinion But yes, the germans do have some fantastic zoos. The ones that springs to mind straight away are Leipzig Zoo and Hannover Zoo.
Those are fantastic, but other great zoos in Germany include: Berlin Zoo, Berlin Tierpark, Hagenbeck Tierpark, Walsrode Birdpark, Zoo am Meer, Duisburg Zoo, Dortmund Zoo, Wuppertal Zoo, Frankfurt Zoo, Munich Zoo, Nürnberg Zoo and Halle Zoo (just to mention the great ones I have seen).
As I said, this is a matter of opinion. Don't underestimate Germany's near neighbour; the Netherlands. Burgers Zoo, Rotterdam Zoo are my favourite zoos, and also Apenheul and Emmen are worth traveling for.
And then there is the rest of the world also One of the reasons that the german zoos are so high-profiled is that there are a lot of zoo-fans in and around Germany.