Both are Ultra-Large, meant for only Airports that can handle them and meant for the long distance intercontinental flights.
So if the 747-8 has less of a carbon footprint and costs less per seat, it may edge out the A380 in the publics mind IMHO.
The question comes down to the cost/passenger and the volume of passengers on a partiuclar route.
Do you fly 1 of the Airbus 380’s or two of the B747’s?
Airbus is selling them, each one sold is a huge sale for Airbus, and a huge loss for Boeing.
Boeing SHOULD be able to compete, carbon fiber and other light-weight materials, better engines, sophisticated electronics and robotic assembly all working together to make stronger, lighter, faster and more efficient aircraft.
When it comes to innovative designs - I tend to look to American ingenuity. Anymore, we are seeing it come from someplace else, first. That’s a disappointment.