Um, it practically popularised the Chocobo, as well starting the whole "De Chocobo" song theme, starting with Mambo De Chocobo.
And yes, Gilgamesh began here. Battle on the Big Bridge anyone?
All of this.
Plus, the Job system is pretty freaking awesome...I mean seriously! I ended up subbing DNC quite a bit and it worked out wonderfully. The job system is what got me seriously hooked on playing it.
The storyline though...yeah, not so much.
I only want your happiness...even if I may never be yours to share it.