I remember playing Metal Gear on the NES and there were no new MG games until Metal Gear Solid arrived in 1998 for the PS1. Playing MGS 5 gives me an eerie but satisfying feeling of coming full circle to where the current (Punished) Snake becomes the legendary enemy, Big Boss, whom you fight in the Nintendo version. Also, after I saw an image of an expanded mother base, it looked just like the base Snake infiltrates in MSG 2 for the PS2. Did the developers intend that the Mother Base that Big Boss/Snake builds in MSG 5 is the actual base the other Snake infiltrates in MSG 2?

The visual appearance could be an homage to the Big Shell, but it's definitely not the same facility. The base you build in MGSV is located off the coast of Africa. The Big Shell is built in New York Harbor to clean up the oil from the tanker that sinks at the beginning of MGS2.

Pretty sure the NES got a sequel, though like the NES version of the first MG it's not the same as the MSX2 original. On a sidenote, you should totally play the original MG1 on the MSX2, still holds up now while the NES version hasn't aged well.