At three trips to the World and so many restaurants untried, I wouldn't presume to pick "the best" but I'll give you my personal five best:
Victoria and Albert's
California Grill
Boma
Kona Cafe
Brown Derby
Special shoutout to Flyng Fish-- can't rank them because I never had a full meal there but did appetizers and cocktails at the bar once and thought the appetizers were incredible.
Still waiting to try Jiko and Citricos-- those are the big "foodie" joints that are next on my list.