Take a look at the SQ 777-300ER's - which are configured like the A380 - with the same business class seats (42 vs 60 on the A380) and are operated on similar long haul routes (SIN - FRA & CDG).
They seat ONLY 278 Pax NOT 360.
So redo the fuel burn comparison with 278 seats vs 471 and you will see a different story.
This like for like comparision shows that the A380 carries 70% more pax than the 777-300ER. So in fact it makes sense for routes that don't support 2 full 777-300's, but with the better economics it still makes sense even of you only fill the A380 to an 85% load factor - the equivalent of 2 777-300's. Even with 85% load factor - 405 Pax the fuel burn per seat numbers are similar to the 777's.
And of course on high density routes where airlines are slot limited (like at LHR) it carries 70% more pax for the same number of slots - this is what is was designed for and what most of the customers have ordered it for. It's no coincidence that LHR expects to see more A380's than any other airport.