You ask a hard question.
Obviously, we don't know what the Phantom Pain holds for this particular period, but in Chronological order in the METAL GEAR series:
1. 1963/64 MGS3: Snake Eater (PS2)
2. 1970 MGS: Portable Ops (PSP)
3. 1974 MGS: Peace Walker (PSP)
4. 1975 MGS: Ground Zeroes (8th Gen)
5. 1984 MGS: The Phantom Pain (8th Gen)
6. 1995 Metal Gear (NES)
7. 1999 Metal Gear 2: Solid Snake (NES)
8. 2005 Metal Gear Solid (PS1)
9. 2007/2009 Metal Gear Solid 2: Sons of Liberty (PS2)
10. 2014 Metal Gear Solid 4: Guns of the Patriots (PS3)
TPP tells the story of the further dispute between Major Zero/Cipher/The Philosophers/LaLiLuLeLo and Big Boss. Starts Diamond Dogs from the ashes of Militaire Sans Frontier after waking from a coma. He creates his own military nation free from government control. It's the bookend of the stories that focus on Big Boss, and transitions into the stories of the clones, whom have appearances in the game (at least Liquid).