In terms of what is open currently, you might check out Wine Bar George (Disney Springs), Tiffins (Animal Kingdom), Hollywood Brown Derby (Hollywood Studios), California Grill (Contemporary resort), Topolino's (Riviera resort). Chefs de France in EPCOT always feels fancy to me. Also several nice restaurants in the Swan and Dolphin resorts: bluezoo, Il Mulino, Shula's.
Not currently open but worth checking out if they do: Flying Fish (Boardwalk resort), Jiko (Animal Kingdom Lodge), Yachtsman Steakhouse (Yacht Club), Monsieur Paul (EPCOT).