The original Metal Gear Solid (original review) was released in a dual CD case in 1998 on the trademark PSOne "black discs." In The Essential Collection, this title has been transferred to a standard PS2 DVD case that holds both discs of the game. However, Konami instead of transferring the game to the PS2 DVD format, the company managed to re-release the title in its original PSOne format. That's pretty cool, especially since those discs haven't been made for quite some time. The original Metal Gear Solid includes a briefing mode that introduces the action before Snake's mission on Shadow Moses starts, previous operations info that sums up the events of Metal Gear 1 and 2, and VR Training missions.
There is, however, one significant downside to this re-released setup, which relates to the save mechanic. The title only recognizes original PSOne Memory Cards to save your progress; no changes have been made to recognize the PS2 Memory cards in any way, so unless you can track down one of those old cards for a PS2, or you create a memory card on your PS3, you won't be able to save at all. Were this collection held on a single Blu-ray, this would make sense, but since everything is essentially aimed for a PS2 audience, this seems flawed.
Metal Gear Solid 2: Sons of Liberty (original review) was released on the PS2 in 2001, and was the first title in the series on the console. Instead of including the original game, The Essential Collection adds MGS2: Substance (original review), which was released in 2003 and hosted a lot of additional features. These include the more than 200 VR missions that were scattered through four different gameplay modes, as well as alternate missions. Apart from these additional exercises, players can check out the Snake Tales, which provide five additional stories for Snake to explore, as well as unlockable characters and Skateboarding. That adds a ton of replayability to a great game, and getting access to the "Director's Cut" of MGS2 is an excellent addition for The Essential Collection.
Unfortunately, the same can't be said about the final disc in the set. Metal Gear Solid 3: Snake Eater (original review) was released in 2004, and was set earlier than the previous games in the series. Relying more on natural camouflage to help Snake in his missions, Snake Eater shifted the sneaking mechanics for the franchise. The re-release in 2006, Metal Gear Solid 3: Subsistence (original review), added a much improved 3rd person camera, as well as a lot of additional features on a second disc. While The Essential Collection includes MGS3: Subsistence, it only includes Disc 1 of the remake. That means that while players will receive the new camera viewpoint, all of the extras on the second disc have been lost. That means that items such as the multiplayer mode, Duel Mode, Demo Theater, and original Metal Gear games have been excluded from this collection, which is unfortunate. There were hours of additional content thrown into the second disc of Subsistence, which would be great for fans. While it makes sense to remove some features, such as the multiplayer since the service is no longer supported, the other items could've been republished for relatively little cost.