Hmm - one thing about the old gold box games, though, was that although they were set in the Forgotten Realms, it was still 1e, which meant that there was very little color added in the actual systems (i.e. no special abilities depending on deity chosen as in Greyhawk 1e or Dragonlance 1e) - so the Realms were sort of chosen as a "vanilla" world for standard AD&D (fighters, clerics, etc.).
It also seems that some cities that appeared in the games were developed for those games, not the other way around - I remember Curse of the Azure Bonds had a module made for 1e AD&D, converting from the PC game (unfortunately, Secret of the Silver Blades never had that happen, and the town of New Verdigris is still not on any official map it seems
).