Isn't this the NES game?

No, this is the original game that was released on MSX computers in Japan. The larger file size may be due to work done on the game to make it run on modern computers, the story was also re-translated and some of the text does look more high-res then other parts of the game.

The NES version had a lot of changes made to the game which you can read about here:

[url=https://en.wikipedia.org/wiki/Metal_Gear_(video_game]https://en.wikipedia.org/wiki/Metal_Gear_(video_game[/url])

They are essentially two different games due to this.

While I wouldn't mind having the NES version here too, I was very happy to see it was the original. I would be similarly happy to see the rest of the series release here, whenever that might be possible.

A large contributing factor is that the music and sound effects aren't emulated, but rather uncompressed 16-bit/48kHz WAV files. That takes up 60 MB on its own.

Also, it's only 80 MB after installation.

As someone already said, is the MSX original, not the NES one, and is 83kb the game info, and 134.92MB the emu X'D

Oh, I'd love to see the old Metal Gear NES and Snake's Revenge NES come to GOG. That'd be pretty cool, even though those games aren't in the Kojima Universe.

I hope MG2 from MSX comes here to GOG also.

That's not what was said. There is NO emulation.

This version is not emulated. This one has it's roots in a mobile port that was then the basis of the ps2 version. It's not bad for what it is, just be warned that the gameplay is choppier than the original.

If you don't me asking - are there any other differences b/t this mobile port and the original?

This comes from the Metal Gear wiki:
----------Nintendo Entertainment System---------------------
The NES version of Metal Gear was developed shortly after the completion of the original MSX2 version, although it was developed by a separate team without the consent or involvement of Hideo Kojima or any of the original MSX2 staff. Many substantial changes were made to the game during the conversion process, resulting in a drastically different game. Up until the inclusion of the MSX2 version in Metal Gear Solid 3: Subsistence, the NES version was the only version of the game that was officially available in North America.

----------Mobile phones---------------------------------------------
A mobile phone version of Metal Gear was released only in Japan on August 18, 2004. The game is based on the original MSX2 version, but includes several additional features and changes.

New Easy mode - The player can choose to play with the original MSX2 version's difficulty or with an easier difficulty setting.

Boss Survival mode - After clearing the game once (regardless of the difficulty setting), a new game mode is unlocked, in which the player can fight against all of the main game's bosses. The player will be awarded with a title based on their clear time (this is also the case in the main game).

Infinite Bandana - A hidden item that becomes available to the player after clearing the game once on either difficulty setting. Like the bandana featured in Metal Gear Solid and Metal Gear Solid 2, this will conserve the player's ammunition to the present amount while firing.

Rewritten script - The Japanese script has been rewritten to include hiragana and kanji, in addition to romaji and katakana.

Name changes - Several of the game's characters had their names changed in the mobile phone version:
Dr. Pettrovich was changed to Dr. Drago Pettrovich Madnar.
Elen Pettrovich was changed to Ellen Madnar.
Shoot Gunner was changed to Shotmaker.
Arnold was changed to Bloody Brad.
Coward Duck was changed to Dirty Duck.

Removal of passwords - The passwords that are featured in the MSX2 version have been removed. The passwords unlocked several things.

----------PlayStation 2-----------------------------------------

A PlayStation 2 version is included as a component of Metal Gear Solid 3: Subsistence. The game includes all the changes made in the mobile phone version, as well as further enhancements. The English version contains a rewritten script as well, with a more complete translation than the earlier European MSX2 version. The North American version also has an optional Spanish script. It also includes some sound effects that were originally present in the MSX2 version of Metal Gear 2, including the high pitched squeak that's uttered when a boss is hit, as well as the higher pitched version when their health is dangerously low upon being hit. It also contains descriptions for the various weapons which had been left out of the original localization.

----------Wii Virtual Console-----------------------------------

A port for the Wii Virtual Console was released on December 8, 2009 for Japanese players only. It was primarily based on the MSX2 version instead of the NES version.

@Rockman
That is really informative and very helpful. Thanks for the information.
Very much appreciated.

It looks more like the redone version included with one of the mgs3's either subsistence or snake eater, I'm not sure, but that version has official translation, whereas the original msx metal gear had broken English translation

Upon some further testing, the installation size can be reduced to 52 MB with no quality loss if you convert the soundtrack files to mono, as it's just dual mono anyway. The game plays the mono files just fine, so I don't know why they bothered making them stereo and wasted 28 MB.

Any chance to make the game less laggy? It runs at about 17fps now...