Three Big Things:
1. Arguably the oldest individual identifiable by name in all of known history. If you read every biography ever written in chronological order, his will be first.
2. Formed the first real empire in all of human history (Mesopotamia) – a civilization made up of different peoples and cultures but still forming a coherent whole.
3. For centuries after his death, his military success, his rule as king, and his general self-proclaimed awesomeness set the standard for all subsequent generals and monarchs. He was Alexander the Great, Napoleon, and Patton, all rolled together. (Or was he?)