Metal Gear 1 and 2 for MSX are the true Metal Gear games. The MG1 on NES is a port job of MG1 for MSX and MG2 on NES is an entirely different (and shitty) game.
All hail MSX. The MSX version of Gradius/Nemesis also fuckin rocked. And had some kind of extra DSP in it. Starfox style. Although, not for 3D obviously.
Yeah it's been ported to Japanese cellphones with brand new Yoji Shinkawa character art replacing the pseudo-moviestar pics in the original. It also has boss rush mode and extreme mode after beating it.
BTW, MG and MG2: SS are on the MSX2, not the MSX. And you can try them out on emulator, or watch the speedrun videos. I found MG for $100 in Japan last summer, and MG2 was going for $200.