Yeah, "converting a D&D Campaign into an RPG" is actually pretty impressive for an NES game. Really, I always felt it was relatively polished an entertaining for its time. I mean, most other RPGs at the time were trying to pull that off, especially on home computer, and I always felt like what we got were inspired in the right ways while streamlining enough that it didn't become a total slog like many of its contemporaries.
Really, FF2 might be historically important, but if I didn't know all that, I'm not sure I'd even bother finishing it, whereas I rarely lost motivation with the original FF, even on the NES.