I would suggest Jiko, California Grill or Citrico's for a romantic Anniversary dinner at Disney. If you have the $$$$$ I would pick Victoria & Albert's. We dined there for our 10th anniversary and it was the highlight of our trip.
Victoria & Albert's is a very romantic and intimate place to dine. My DH and I have been going there every year for the past 3 years to celebrate our -and a half anniversary- our actual one is in March. The food is great and the atmosphere is lovely. So if you want to splurge this is definitely the place.
We just celebrated our 25th with a quiet, intimate dinner at Artist Point. DS and DDIL celbrated their first anniversary at California Grill. DS said it was too loud and bustling for him, not quiet at all. However, they had lunch at YCG one day. Wonderfully restful, quiet resturaunt. He commented that he would have had a better time going there for their anniversary!
Another vote for Artist Point. WL also has the Territory Lounge which is a nice & relaxing setting to either start or finish your evening with a drink!
After V&A's my choice for such an occasion would be Artist Point. Wonderful atmosphere, adventureous menu, interesting wine list. After the meal, take a walk down to the lake-front and wait for the geyser to go off on the hour.