Palais de la Méditerranée probably, but I'd prefer to stay 'near' rather than 'in' so like the Chateau De La Chevre d'Or in EZE and Le Saint-Paul in Saint-Paulas well as Chateau St-Martin in Vence.

Although probably not 'best' any more the newly refurbished Negresco just might regain the title. I hope so. That's my emotional favorite in Nice.

I know TrophyCollector knows the area well, but the poor person simply does not know what a 'declining city' is. Nice is not one.