The MSX version is known to be much better than the original NES version. The MSX version is the only version Hideo Kojima endorses, he had nothing to do with the NES port he said.
The MSX version of Metal Gear 2: Solid Snake is known to be very good also. The only other way to play it is on PS2 in the Metal Gear Solid 3: Subsistance DVD.
Also, don't suggest downloading ROMs as that is illegal and could get you banned from the forums. Say, "You should check Metal Gear for MSX" and that is the best you can do on here.
There is also a Metal Gear skin for blue MSX called blueGEAR, check out my link.
blueGEAR