I've owned pit bull dogs, mini schnauzer, I have a pomeranian/Shih-tzu, and I'v fostered lab, beagle, pit bull, collie mixes.
The differences I've noticed between GSD and all of the other breeds is the ease of training. They are smart as a whip and 'doggedly' loyal. They are very dependent, want to be right next to you 24/7(I woke up this morning with J's head on my pillow lol).
The others were more difficult to train... They were not as focused on me. I'm not saying they did not want to please, they were just harder to train, less obedient, and some (hounds mostly) were more independent.
My current other breed, the pom mix, is very, very smart, she wants to please, but she's stubborn and more independent, she is FINE with being left alone, doesn't phase her a bit, whereas the GSD wants to be glued to me and doesn't like being left alone for any period of time (not anxiety, but not happy).
But saying "they're not like any other dog I've owned" can go for most breeds... APBTs are not like any other breed I've owned... My pomeranian/shih-tzu is not like any other breed I've owned, the Schnauzer was CERTAINLY not like any other breed I've owned... The Lab/beagle/maybe pit was not at all like any other mutt I'd owned... All breeds have their own traits, and that in itself makes them unique. German Shepherds are famous for their loyalty, bravery, and protectiveness(among other things), APBTs are for their tenacity, loving nature to humans, and goofy attitudes, Daschunds for their big attitudes in a little body... ect. ect. ect.