Many of the gameplay innovations commonly attributed to Metal Gear Solid were in fact introduced eight years earlier by its direct predecessor Metal Gear 2: Solid Snake, which was never released outside of Japan until it was packaged with Metal Gear Solid 3: Subsistence in 2006. As such, Retro Gamer regards Metal Gear 2 to be "as close as anyone can get to playing Metal Gear Solid in 2D." Many fans also believed that Metal Gear Solid was a remake of Metal Gear 2. Some of the gameplay and plot elements in Metal Gear 2 that were later used again in its sequel Metal Gear Solid include:
- The game opening with a cliffside open environment before moving inside to a tank-storage room with an elevator.
- Roy Campbell serving as the main commanding officer to Solid Snake.
- Master Miller (impersonated by Liquid Snake in Metal Gear Solid) giving advice on improving one's health and professional life.
- Saving a hostage who appears on radar. In addition, the first hostage of the game is a disguised member of the terrorist faction.
- Snake has to rescue a female contact (both with the frequency 140.15) after her cover is blown, is sneaked up on by the contact (in disguise), and eventually becomes romantically involved with them (Holly White in Metal Gear 2 and Meryl Silverburgh in Metal Gear Solid).
- Meeting a disguised female contact in a women's washroom (Gustava Heffner in Metal Gear 2 and Meryl in Metal Gear Solid).
- Helpful messages from an anonymous source via the radio claiming to be a fan of Snake, who turns out to be Gray Fox in both cases.
- An ally from the previous game betrays Snake (Dr. Madnar in Metal Gear 2 and Master Miller in Metal Gear Solid, which was actually Liquid disguised in the latter game).
- The use of the line "It's not over yet, Snake!" Big Boss said this in Metal Gear 2, while Liquid said this in Metal Gear Solid.
- While escaping the enemy stronghold, Snake and his companion are nearly killed until they are saved at the last second (Charlie saves Snake and Holly in Metal Gear 2, while Liquid dies from FOXDIE in Metal Gear Solid).
- The return of a major character from the former game decked out as a ninja (Kyle Schneider in Metal Gear 2 and Gray Fox in Metal Gear Solid) who must be fought in a boss battle.
- The return of a major character presumed dead in the previous game returns (Kyle Schneider and Big Boss in Metal Gear 2 and Gray Fox in Metal Gear Solid) and is fought in a boss battle.
- An ambush by four hidden attackers in an elevator.
- A fight with a boss wearing stealth camouflage.
- A chase up a spiral staircase with soldiers in pursuit.
- A battle with a Hind D chopper using Stinger missiles.
- Fighting a piloted Metal Gear (Metal Gear D in Metal Gear 2 and Metal Gear REX in Metal Gear Solid).
- After destroying the Metal Gear of the game, an unarmed hand-to-hand showdown with the pilot will take place (Gray Fox in Metal Gear 2 and Liquid Snake in Metal Gear Solid).
- A one-on-one fight between Snake and Gray Fox in both games.
- An escape from the enemy base alongside a female accomplice (Holly in Metal Gear 2 and Meryl in Metal Gear Solid) while being chased by a horde of enemy guards.
- Having to look at the back of the game package to learn an important radio frequency.
- Having to use plastic explosive on a door in order to reach a new area.
- Having to change the temperature of an object to turn it into a key.
- Having to heat up frozen rations before eating them.
- After meeting up with Snake, a female accomplice will discard their disguise while revealing why they did so (Holly complains that it is too tight on her chest in Metal Gear 2, while Meryl claims that it smelled like blood in Metal Gear Solid).
- After Snake meets up with a disguised female contact, he will make a comment about the impracticality of the gun that they are using.
- Having to find and/or kill an animal or animals that has a key item.