Only one? There is no way.....
But if I have to logically break down my thought... I will pick -
CA Grill - if I never have any Asian fusion food (ie, if you live outside of LA and NY).
Flying Fish - if you love seafood, served in a fun (aka, loud) environment.
V&A - if you love romantic scene, want to go all the way out, and rich.
Brown Derby - if you love great food while dressed in a T-shirt, and happen to be in MGM and must make Fantasmic.
Akerkraus (Norway) - if you really want something very, very unique.
Tenpayaki or Moroco or Matsu no Ma - If Norwegian food freaks you out, but still want to try internationally unique food.