Metal Slug X is an enhanced version of Metal Slug 2: Super Vehicle - 001/II. The main differences to the original release include:

• Additional weapons: Stones, Iron Lizard, Enemy Chaser, Super Grenade, and Drop Shot.
• Additional power-ups, items, and prisoners in most of the levels.
• Additional times of the day: stages can take place at twilight, sunset, or dusk.
• Some of the locations and vehicles in the game have been altered.
• Increased enemy count. Some of the enemies' placement has been changed.
• Many weapons have a stronger explosive force. Explosions yield more unexpected results.
• The soundtrack has been re-mixed.