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.
Thanks for stating the obvious and managing to not answer my question at the same time.