I would split the brands into two "luxury" classes:
Cream of Crop, 5-Star:
Mandarin Oriental, FS, Ritz-Carlton, Rosewood, St. Regis, Park Hyatt, Peninsula, Aman Resorts
4-Star Plus:
Waldorf, Conrad, Fairmont, InterContential, Shangri-La, Taj Hotels/Resorts, Langham