Fuel Efficiency of the 787 Dreamliner
It would be unfair to compare the 787 Dreamliner with the Airbus A380 in terms of fuel efficiency as this would be comparable to comparing the fuel efficiency of a passenger bus to a full size van. But in layman's terms, the fuel efficiency could be computed as follows:
Fuel Efficiency = Fuel Capacity / (Max Range * Max Capacity)
The 787 Dreamliner has a fuel capacity of 33,528 U.S. gallons. Max range is 15,200 kilometers with a maximum capacity of 250 passengers. Based on the given information, the fuel efficiency is expressed as 0.00882 U.S. gallons per kilometer per passenger.
The Airbus A380, on the other hand, has a fuel cpacity of 81,890 U.S. gallons and a maximum range of 15,200 kilometers. Maximum capacity is rated at 853 passengers. This would give a result of 0.00632 U.S. gallons per kilometer per passenger.
Remember that while the A380 still yields a lower cost per mile compared to the 787, the above figures assume that the aircraft is flown within the maximum range while carrying the maximum amount of passengers possible.