On his Facebook page, Gunn posted “Phew. After 48 days straight without a day off, the the first draft of #GotG2 is done. I’m sorry to all my friends and family who I have ignored.”

On his Facebook page, Gunn posted “Phew. After 48 days straight without a day off, the the first draft of #GotG2 is done. I’m sorry to all my friends and family who I have ignored.”
Technically, he should have used a “Screenplay by” credit, since he did not come up with the Guardians of the Galaxy story. Despite being very unique, he borrowed from the rich tapestry set forth in the comics, and certainly added in his own stuff here and there, but still didn’t come up with the original idea.
“Written by” is if the idea is his. Most (if not all) adapted screenplays are not written by the original creators, therefore almost always the writers get a “Screenplay by” credit.
Shame on you, James Gunn!