Some personal 'bests' of mine:
Best overall: California Grill (excellent food, wonderful views and observation deck fireworks in the evening)
Best food options: Le Cellier and Monsieur Paul
-Le Cellier (excellent food, although it is crowded and tables are close together and it can be noisy, which ruins the romantic setting in my opinion).
-Monsieur Paul (recently ate here and had an amazing meal. However, for a quieter and more romantic and intimate dinner, go early before it gets full. It's quite lovely inside and I'm not sure why it isn't liked more)
Best non-signature restaurant: Sanaa (at the Kidani Village at Animal Kingdom Lodge...flavors are slightly exotic but very approachable. It's a cute/nice setting and not as formal as the others...and you can check out the nice hotel and the animals on the savanna. If you want more romantic and upscale, Jiko is an excellent option, but it is a signature restaurant.
Best for romantic atmosphere: San Angel Inn (perhaps not quite up to the level of signature dining food, but the meals are still really good, and it is perhaps my favorite restaurant in terms of atmosphere.