It's an old story, the MSX version of MG was fantastic but then apparently hopelessly ported to the NES in a short space of time and outside of the control and oversight of Kojima....
But you know what... I have played the MSX version, I've played through it, I've tried to complete it, but imho, for all the supposed inadequacies of the NES version, I actually prefer it.
I prefer the fact that you have to infiltrate the base at the beginning, that is fantastic! People love MGS3 for that reason and I think it is a great touch. In the MSX version.... meh.... you start out in the base already.... not very sneaky.
And as to the fact you don't fight Metal Gear? SO WHAT? Why should you? I actually thought it stupid in MGS that you actually fought Metal Gear, it is meant to be a mobile device that fires nukes.... not something designed for combat with a single man. It stands to reason that it makes more sense to destroy the computer that controls the thing and also the man who is operating it.... which is exactly what you do in MG Nes.... Imagine someone having a fight against an ICBM machine, that would be dumb, it wouldn't be an opponent... it would not be geared up to fight you, and you would be able to take it out easily.... so that's why it doesn't matter that you don't fight Metal Gear.
And above all.....
The MUSIC in the NES version is absolutely superior! The MSX music is painful, dull and something to mute as soon as you can. The NES music is fantastic! It is exciting, it is tense, it is an amazing score and whoever produced it should be proud of themselves.
I could write more on this, but I need to prepare to offer Holy Mass, which isn't in 5 mins, but in 30 mins by the way. Priests should prepare for Holy Mass properly.