Given that it is a thirsty bird with four engines burning compared to say the B777 or B787 or A350?
Of course it is more thirsty, it is bigger.
If fully loaded and on the mission it is designed for, the a380 burns
less fuel per passenger than the 777. 787/A350 are newer design with newer technology, so they do indeed burn less per passenger.
It is
not the number of engines, and if exceeding a certain size, there is no other option than having 4 engines.
Given a choice between economy in a 787 and an A380 I know which I would rather travel in.
Given the choice between a non-stop flight on a 787 and a flight via a hub to fill an A380 I would exactly know what I would travel in: In the A350 nonstop
But since the A380 is a double deck above, it carries far more people so that lower lobe is filled with much more luggage, leaving little space for freight.
There probably is agood reason (or actually two more...) why Boeing never changed the 747 to full double deck. Looking at the dreamlifter, they may have been able to do so, but actually it does not make sense.
Airbus once had a major market advantage for the A300 compared to the Boeing products, because they offered more cargo space which allowed the airlines to do additional profit. On the A380 they did the opposite, and it hurts. Initially they went for a conventional environmental control arrangement, but later moved it to the wing roots to gain some more cargo space. They also (compared to the 747) selected a body gear arrangement which allows additional cargo space between, still it is not that much.
That is why Boeing is going to fold the wings on the 777.
They still have to proof that this does not only look like a clever design, but actually works in real service life... Adding complexity rarely pays off.