Actually Guardians 1 did as total boxoffice of 774 million. Guardians 2 did as total boxoffice of 864 million. So yes he gave them (so far) 2 films with a total boxoffice over 1.6 billion. Considering these were Gunn's first major motion pictures (he did indie films like Slither and Super before this) its good work.
I was reading older numbers...but yeah, they have reached the Magical Threshold (1 billion +). GoG is a solid property and in the elite billion dollar club. Look at Shrek. They should have ended that story at the second movie, but Disney decided to continue with the series and a new one will be coming out in 2019. The series Once Upon A Time was spiritually ended at the end of Season 6, but Season 7 is already being aired using a soft rebooted premise. These Disney properties are ultimately corporate assets.