To me, a truely luxurious hotel room must have these attributes.
Space, lots of space, well designed open space and if a multi-room suite, each room must feel spacious. Not just physical space but a sense of space. In other words, no slanting walls, low ceilings, rooms crammed each inch with useless furniture. Small = Not luxurious my books so don't tell me a shoe-box room like 25sqm is luxurious even if it's the Ritz or Four Seasons. My room requirement starts at 45sqm although I will tolerate a 40sqm in some occasion. Outdoor balcony and terrace adds to the sense of space and are a big plus.
Decor - As in well designed, pleasing to the eye, and must use very high quality materials. Things in the room must feel well made and well maintained. Rooms with ikea like cheap furniture just doesn't cut it. Abundant natural light. I can appreciate both modern contemporary and classical decor, as long as it's tastefully done and luxuriously furnished. Large windows. Preferably floor to ceiling.
Style - That's very subjective. Everyone has different taste. What is stylish to one is not stylish to another.
Comfort - A must, and that includes things like a good air condition, sparkling clean, smell good, a great bed for a great night sleep. shower with strong water pressure. These basics must be well taken care of. IMO, a room that is not comfortable is not luxurious. Double glazed windows and thick walls to keep off intrusive noise. A truly luxurious hotel room should be something you look forward to return to relax in, or even better enjoy being in it and not want to go out! If it doesn't, it's just another hotel room.
Amenities and equipment - Thick fluffy Bath towels and bathrobes, slippers, coffee machine and coffee making facility ( a must for me ), large screen high-def television, iPod speaker, generous supply of complimentary drinking water. Plugs / USB plentiful and conveniently located to charge my stuff. An actual work desk. Fast Internet. Generous welcome amenities.
And lastly, of course, warm, efficient and friendly service to match.
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