During an earnings call, Take-Two chairman and chief executive officer Stauss Zelnick stated that Borderlands 2 is 2K's best selling game of all time, with 8.5 million copies moved to date.
Here is the full statement:
"Borderlands 2 is a prime example of how we are able to generate substantial revenue and profits from add-on content over an extended period.
"In the 16 months following the title launch, we released nine substantial downloadable offerings, dozens of smaller character customizations, and we have plans to release more downloadable content in the coming months. This is an addition of package good, add-on packs, and most recently, a Game of the Year Edition."
"The popularity of add-on content for Borderlands 2 is an important contributor to the title’s becoming the highest selling release in history of 2K with more than 8.5 million units sold-in to date."