Some companies try making "luxury cars" by just rebranding their normal cars, adding some chrome or gold plating, maybe some extra equipment, leather and so on but in the end we all know what they're all about.
Hyundai trying to push their "Genesis" luxury brand - as much as I hate to admit it - are possibly the only ones that are doing it right even though my feeling is that even a luxury Hyundai will remain a Hyundai.
The other for example Honda, we all know that an Acura TLX is more or less a Honda Accord.
The same way we know that an Infinity G35 is more or less a Nissan Altima and that a Camry is more or less an ES350.
For these reasons I believe that we still can't have a "luxury" brand from a company that started out by making "people's cars" like Kia, Hyundai and even Toyota, Nissan or Honda, as nice as their upscale Lexus, Infinity and Acura brands are I think it's a matter of perspective.
Was the car created from the ground up to be luxurious or is it derived from another car the company sells for less to a cheaper crowd? If so then it's not a luxury vehicle as the whole point of being exclusive goes out the window the second you reuse parts.
Brands that were born luxurious are the only ones IMHO that can be called luxury cars.
In Europe there are BMWs and Mercedes, they are born luxurious, do not share parts with Mazda or Ford unlike Volvo who claims to be luxurious, but as nice as a Volvo is, the moment it shares any parts with lesser rated platforms it dilutes it.
In America we have Lincoln and Cadillac, although Cadillac's new models 2013+ as nice as they are, share their platform with the Camaro. The 1st and 2nd gen CTS didn't share their platform. Was it a perfect platform? No. It's big and heavy but it's only used for other Cadillacs = luxury.
Same goes for some of the BMWs and Mercs. If they share their platform among other BMWs and Mercs then it's fine, but if like some of the Mercs like the B class models, you share your platform with VW or Nissan then sorry but what you have, as nice as it is, is not a luxury car.
Lastly do not confuse luxurious with performance or fast.
American cars have had two decades of making shit "luxurious" cars, Cadillacs from the late 1980s up until the mid 2000s were really REALLY shit cars nobody wanted.
They've come back from that now, so has Lincoln although they've not had as much success as Cadillac.
Anecdote? Why not. Look at who's post this is...
When we go to family gatherings some of our family members have Mercs and Infiniti, some have Acuras and a few Volvos and at least one has a BMW, yet no other car brings as many questions from others as the CTS. From how much gasoline it uses to the ride quality, cost of maintenance and reliability, and so on.
I think that defines luxury. It means you've achieved something and you can have nice things.