...is no such thing as a Sumerian Epic of Gilgamesh. While there are a few Sumerian poems featuring Gilgamesh or Bilgamesh, what is known as the Epic of Gilgamesh was composed in Akkadian, a completely different language (as different as Chinese and Japanese). For more information, I recommend Andrew George's Penguin Classics version of the Epic of Gilgamesh (and related texts), or, for the really adventurous (and wealthy or living near a good public library), his edition, translation and commentary of the original cuneiform texts, published by Oxford University Press. It should be noted that new fragments have come to light since the publication of this standard edition.