As an owner of German shepherds, I see both sides. The three we have owned have been wonderful, loyal, and smart dogs, but can also be a handful and "aloof" if not properly trained and socialized. That is just who they are.
They are very, very protective of their "people" and their homes.
Frankly, city/apartment living is not a great idea for them in general. I'm not saying it can't be done, but they are far better suited for large outdoor areas where they can constantly be challenged both physically and mentally.
They also shed quite a bit and can wreak havoc on homes. I can see why a landlord wouldn't want them (not to mention the potential liability). As many know, some insurance carriers will ask about breeds in a residence, so it's likely that it's the landlords insurance restrictions that might be causing this.
I think most people would agree it's a good idea to do your research on a breed, talk to other owners, and make sure you understand up-front pros/cons, and what the limitations might be for owning a certain breed.