The Epic of Gilgamesh and Genesis both contain stories of a flood that wipes out almost all living things. Compare these stories and their...

The stories are very similar, but contain minor
differences. As humbahaha pointed out, the Genesis flood is sent because of humanity's
wickedness, while the Gilgamesh flood happens due to mankind becoming too numerous and
noisy ("Enlil heard the clamour and he said to the gods in council, 'The uproar of
mankind is intolerable and sleep is no longer possible by reason of the babel.'").
Additionally, the storm in Gilgamesh pours down for six days and six nights, compared to
the 40 in Genesis. And while Utnapishtim sends a bird thrice from his boat, Noah sends
it 4 times - it returns the third time with an olive branch, and the fourth not at
all.

There are, of course, other differences dealing with
the end of the story, as Utnapishtim gains immortality and Noah is told to repopulate
the Earth, etc.