The Metal Gear Solid games span across decades, though not in chronological order. This should clear the timeline up.

As Solid Snake infiltrates Outer Heaven, the player intrudes upon the game’s world. Neither are welcome, and if they’re caught, they will be destroyed. Metal Gear 2: Solid Snake’s defining ...

However, the saving grace of Snake’s Revenge is that after hearing about its development, Kojima was inspired to create a true sequel to Metal Gear 2 – Solid Snake. These ‘true’ versions ...