Wikia

Metal Gear 20th Anniversary: Metal Gear Solid Collection is an Japan only collection that was released to celebrate the 20th anniversary of the Metal Gear series. It was released on July 26, 2007. The set costs ¥6,900 (roughly £28, or $57).

The collection includes:

Metal Gear and Metal Gear 2: Solid Snake (on one PlayStation 2 disc)
Metal Gear Solid
Metal Gear Solid 2: Sons of Liberty
The Document of Metal Gear Solid 2
Metal Gear Solid 3: Snake Eater
Metal Gear Solid: Portable Ops (in a special UMD case)
Metal Gear Saga Vol. 2

The set also contains a special letter from Hideo Kojima, which says the following:

"Metal Gear, my first game, was born in 1987, back when we were still living in the Shōwa era. I remember that at the time, I had no intention of creating a sequel or a series. I was simply hell-bent on making a good game. Today I realize that Metal Gear has made it to 20 years thanks to the support of all its fans around the world. Furthermore, I feel it is entirely due to those fans who love Metal Gear that I have come this far over the past two decades. We created these 20th anniversary versions during this commemorative year as our way of saying thanks to you. The different games each reveal everyone's thoughts and feelings at the time, containing the fingerprints of the period they come from. We hope you enjoy the Metal Gear saga."

— Hideo Kojima