I fail to see the reason for all the comparisons being made between the B777 and the A380. The aircraft are poles apart category and range wise.
As far as payload/range is concerned I have heard mixed views on the A380, especially over LAX-MEL. I must admit the A380 payload of 66 tonnes looks to be on the "skinny" side. (B747-8F is expected to be 140 tonnes).
No doubt we will hear from QF pilots after the aircraft goes into service.
Tim Clark says the endurance of the EK A380's is 13-13.5 hours. (Flight Int 29 July - 04 Aug 2008).
Boeing information shows the following.
The B747-400 can do LAX-SYD (416 pax)
The B747-400ER can do LAX-MEL (416 pax)
The B747-8I is expected to do LAX-KGI (468 pax)
The B777-300ER can do LAX-KGI (368 pax)
The B777-200LR can do LAX-Rottnest Island (301 pax)
Unless you need the longest range airliner available (B777-200LR) the B777-300 appears to be the most efficient.