You are likely to receive a plethora of opinions on this one.
DW and I have eaten at all three many times, and I think that the key to your question is that you want a "romantic" dinner.
CG is certainly an excellent restaurant, with excellent food and a fantastic view (ask for Gary K. the waiter - from Hawaii. Top notch all the way). It does provide a great view of the MK fireworks from the observation deck, and it does have that "special" feel to it, but I wouldn't call it "romantic." It tends to be a bit loud, a lot of hustle and bustle, noises and conversation from the open kitchen...and pretty crowded.
Citricos is very nice, but nothing special or romantic. You will not be disappointed in the food (although it's less "wow" than the other two under consideration), but since it's on the main floor of the GF, you are more likely to have families and more small children (probably not quite the "romantic" setting).
Which is why I would vote for Narcoosee's. First, it's away from the crowds and located in its own, separate building. You can enjoy a nice romantic walk through the GF grounds to get there, it's right on the water, it's quiet(er) than the other two, and the food can be downright fantastic (all the fish selections are very fresh and the steaks, we have found, are sometimes overlooked but are as good as those at Le Cellier or Yachtsman's). Plus, you can relax after dinner on the porch by the water with a cordial or glass of port and watch the Electrical Water Pageant and/or the MK fireworks or simply watch the Disney boats making their way across the lake. We think it's a real hidden gem, and the most romantic of the three you mentioned.
In any event, you cannot go wrong with any of your choices because each of these three restaurants is special in its own way. Enjoy!