I have played all versions, even unofficial ones (don't get nitpicky with me because there are 500 obscure fan translations).

I would say that there is a three way tie between the common fan translation and the PS1 version.

Some of the liberties they took with the fan translation bothered me. Most notably pop culture references (William Shatner should never be mentioned in a FF game).

The PS1 would win outright, but the load times were pretty terrible. Well, to be fair, it was mainly loading the game and saving to the memory card that was the biggest problems, otherwise the game ran fine.

The PSP and DS versions are very cool, but the feel more like remakes to me, especially the DS version. By my own definition, I can't really consider that the best in a weird way.

The US "FFII" version had plenty of translation issues, and it was dumbed down, but it isn't this huge travesty anymore that people make it out to be. Square-Enix has done more than enough ports and remakes to make up for it. The US version has a certain charm to it, and it's fun to play it still just to take a look at the changes and how far things like localization has come.

The GBA port was cool at the time for the added content and spruced up graphics, but it was basically a Wonderswan port that was awkwardly jammed in a GBA cart. The music quality suffered, as well. Plus, all the cool content can be found in the PSP port.

Long story short, if FFIV was a woman, I would stick my dick in her.