I will start this off with I will only be covering the originals not the remakes or ports to the newer systems.
First I will explain this: The NES is the U.S.A NINTENDO. The Famicom is the Japanese NINTENDO. The S-NES is the U.S.A version. The Super Famicom is the Japanese version.
History :
FF I - came out for NES & Famicom.
FF II- The real FF II came out only in Japan for the Famicom.
FF III - Are FF III for the S-NES is really FF VI for the Super Famicom. The real FF III came out only in Japan for the old Famicom.
FF IV - Now here is where it gets confusing but I will explain it. In Japan they got 2 versions of FF IV . They got FF IV Easy Type & FF IV Hard Type for the Super Famicom. We got FF IV Easy Type translated into English for the S-NES & it was renamed FF II.
FF V - Only came out in Japan for the Super Famicom.
FF VI - FF VI came out for the Super Famicom in Japan. We got a English translated FF VI that was renamed FF III for the S-NES.
They now are all available thanks to imports & remakes with the newer systems.
S-NES - We got FF II for S-NES . Which is really FF IV Easy Type for the Super Famicom.
S-NES - We got FF III for S-NES. Which is really FF VI for the Super Famicom. ********************************************************************************
For Japan
Famicom - They got FF I,II & III for the old Famicom.
Super Famicom - They got FF IV Easy Type FF IV Hard Type FF V FF VI All for the Super Famicom.
im still a newbie and learn more things from u guys 
Here is chart.
