The Metal Gear Solid collection will also include the first two Metal Gear games

pcgamer.com:

Konami finally announced the Metal Gear Solid: Master Collection this week, bringing the first three 3D entries in Hideo Kojima's classic stealth series to modern platforms. 'Solid' was always a bit of an in-joke: Not just referring to the protagonist Solid Snake, but to the series becoming 3D. It began on the MSX home computer platform with Metal Gear, and now the official PlayStation store has let slip that the Master Collection will include the first two games in the series.

This is not a huge surprise, because those games (Metal Gear and Metal Gear 2: Solid Snake) were remastered by Kojima Productions itself back in the time of Metal Gear Solid 3, for the Subsistence re-release. They're actually pretty good, especially when you know what came later. The versions of the game in the Master Collection appear to be identical to those in the 2011 HD Collection, and the MGS3 there is Subsistence (which is a good thing, because among other things it added a player-controlled camera). 

Notable by its absence, of course, is Snake's Revenge, a sequel to the original Metal Gear that was made without Kojima's involvement and is generally regarded as an inferior work. Kojima himself has absolutely no time for this entry in the series and disregarded it in all his subsequent work, making it a de facto non-canon entry. Konami is clearly staying on those lines although, depending on where the Master Collection goes from here (this is Vol. 1) it arguably should find a place in any comprehensive collection of the games: Whether Kojima likes it or not. 

The PlayStation listing (thanks, Eurogamer) adds various other little tidbits about the games, including that Metal Gear Solid will come with the VR missions (a standalone title created