I voted for the Rolls, because IMO, Rolls Royce has always been a statement of pure luxury!
But for the most luxurious Cadillac ever, I would have to say the 1974 Fleetwood Talisman, crushed velour 4 place seating, 2 center consoles, The front console contained provisions for an illuminated writing pad with pen and pencil, along with a lockable storage compartment. In the rear is a holder for vanity mirrors and so forth, with the lockable storage bin. Other niceties were deep pile carpet and mats, foot rests and assist straps. Exterior features were a padded Elk grain vinyl roof, special wheel discs, a stand up wreath and crest ornament on the hood, and "Fleetwood Talisman" script on the sail panel.
The Talisman leather package was almost as much as a brand new $2500 Ford Pinto!!!
I would have to say that is one of the most luxurious cars ever!