My two favorites at the resort hotels are Mama Della's at Portofino and Tchoup Chop at Royal Pacific.
We usually do Mama's at least twice on every trip to UO. I have even driven over from Tampa while there on business just to eat dinner at Mama's. The food is the best Italian I have had outside of NYC, and I travel way too much.
Tchoup Chop has great food, awesome service and a really unique atmosphere.