Why millions of people love the 'Metal Gear' franchise

On September 1, one of the year's most anticipated games launched for the Xbox One, PlayStation 4, and PC: "Metal Gear Solid V: The Phantom Pain."

"MGSV" is the final installment in a franchise that's been running for nearly 30 years and has sold just over 40 million copies, starting with the original "Metal Gear" on the MSX back in 1987. And it's all been helmed by a single man: Hideo Kojima.

What is it that people love so much about the "Metal Gear" franchise, that keeps fans coming back across two decades of games?