I've been thinking about this. I'd probably categorise hotels in the following:

Near Private Island level Luxury - Hotels which provide at base level a near private rental experience but with personal Butlers, potentially private chefs or at least private dining venues, etc. and/ or are just ridiculous in some other way
Laucala Island
Necker Island
The Brando
Some of the Oetker Collection hotels which do private hire

Global Luxury: The world's best hotels with the best service
The Connaught
The Dorchester
The Bristol
Le Georges V
The Mandarin Oriental Bangkok
The Peninsula Hong Kong
Villa Feltrinelli
The best Aman's (subject to opinion - candidates include Amanjiwo, Amankila, Amanzoe, maybe Amanpulo)
One or two of the best Indian Palaces - maybe The Oberoi Udaivillas? (not the ones I have been to sadly, even if the Taj Lake Palace is special in its own right)
Some of the top end African Safari camps

High Luxury - Hotels which other 5* hotels look up to
Heavy presence of top-end chains here - Amans, Four Seasons, One & Only, Six Senses (selected properties), the better St Regis, Ritz Carltons, Park Hyatts, SLHs, etc.
Lots of hotels which are best in their market - the Gritti Palace in Venice, the Hotel Les Trois Rois in Basel or the Royal Mansour in Marrakesh comes to mind
Lots of Maldives over-water places

Also-ran expensive luxury
Hotels which are highly priced in their market but which don't meet the standards of the above. These nonetheless sit above the local 5* Marriott.

...And others.

Disclaimer: I've been to nowhere near all of these, particularly not at the top-end which is unfortunately hard for me to justify at the moment.