What made Gilgamesh, from The Epic of Gilgamesh, such an epic hero?

The
difficulty in answering this question is that it can almost be asked in the reverse. Gilgamesh
is, arguably, the original epic hero in world literature. He was the king of Uruk, an ancient
Mesopotamian city famous for its impressive walls, and is regarded as being two-thirds god and
one-third man. His connection to the gods (being two-thirds god and also denying the advances of
the goddess Ishtar and eventually slaying her monstrous bull) and the pure scale of his strength
and achievements help to put him on the level of the epic hero.

He also
undergoes an epic questperhaps the first epic quest ever recorded. Following the death of his
best friend Enkidu, Gilgamesh seeks immortality. In the style of a true epic quest, such as the
search for the Holy Grail or Odysseuss voyage homeward, he faces many monsters and overcomes
many challengesboth internal and external. Though he ultimately fails to find immortality, he
returns to Uruk as a wiser man and a nobler king than he was...