It depends what you consider the original audio mix.
The ORIGINAL release in 1989 only had a stereo mix.
The Little Mermaid was originally released in 1989, before discrete digital soundtracks were commonplace, so the original soundtrack is in Dolby Stereo. The soundtrack was remastered for the 1997 theatrical re-release, but obviously the same sound elements were used, and occasionally the mono effects stand out like a sore thumb. In particular, a segment from a scene where a ship explodes into flame is accompanied by sound effects that emanate entirely from the centre channel.
The original Dolby mix AFAIK has only been released on the laserdisc.
The 1997 5.1 DD remix was very well done, and critics had a lot of good things to say about it (and so do I).
The 1997 mix was release unaltered on the old unrestored DVD in 2000. In fact there was a limited release of the same disc that contained the 1997 DTS mix as well (now THAT would have been wonderful to use).
And as we all know the new Platinum disc only contains the crappy 2006 DEHT mix.
My restored edition uses the 1997 mix, which is infinitely more satisfying.
HomeTheaterForum's did a listening test comparing the 2.0 16/44.1 LPCM (laserdisc), 5.1 DD/AC-3 original mix (laserdisc), 5.1 DD original mix (old DVD) and 5.1 DD DEHT mix (new DVD).