When people talk about Batman Begins being realistic, I think they're talking about how Nolan went out of his way to make every character have motivation, every scene to have meaning, and every part of the Batman mythos to be grounded in reality.
He took fantastical elements, like a terrorist organization that destroys cities, a car that can jump across rooftops, or a doctor who torments his patients with hallucinogens, and gave them purpose, limitations, and rules. And he did it all while setting up a sequel that will (hopefully) require no retconning to make sense.