They never said it couldn't be done... mostly because no one had ever been insane enough to suggest doing it in the first place. But Chinese pirates, regardless, have done the seemingly impossible:
ported a surprisingly detailed and complete version of FF7... to the NES. It's a scary and oddly wondrous thing, in about equal amounts.
[EDIT: Download both game and emulator
here (via MegaUpload).]
Also, from the same site,
finally, I am vindicated on the fact that the literal fan-retranslation of FF6 completely eviscerates the spirit of it.