... and I'm still not convinced 4 x GEnx will burn less than 2 x GE90. That would as good as make the 777F obsolete, whereas in reality it's selling pretty damn good.
Perhaps those GEnx's will burn more fuel, but what about the extra payload that a 74-8 will haul? Take a look at the big picture, not just the FF/Hr per engine.
Actually if you want to compare the 777F with anything, you'd be better off with a 747-400BCF. Both are able to lift around 107 tons, but the 777F can carry the load further. Given a similar load, say 75 tons, the B747-400F will burn 140ish tons on a specific Far East - Europe route. On the same route, on the same day, a B777F carrying the same 75 tons burned 100ish tons. And therein lies the reason why the B777F is the best thing since sliced bread in long-haul cargo, as long as you can live without a nose-door.
Comparing a 747-400 Boeing
Converted Freighter with a 777F (factory build freighter) is comparing apples and oranges and a bit unrealistic IMHO. Of course the 777F will win, it will win hands down because the converted 744 will have a higher DOW and a lower MTOW compared to a factory build 744F.
Comparing a 744F with a 777F (both factory build full freighters) will give a far more reasonable, although still unbalanced, picture, with a 744F hauling a payload of roughly 90 tons and requiring a block fuel of 145 tons to SE Asia. Assuming the 75 tons load and 100t fuel for the 777F that comes down to ±1350 kg of fuel to carry 1 ton, versus the 744F's ±1600 kg fuel per ton payload. Granted, the 777 is a wonderful machine and at the moment has the better fuel consumption (not payload) than the 744F, but again let's be fair, the 777 is a much newer design with next generation engines, sleek wing, raked wingtips, FBW etc.
I'm curious to see how the 74-8 will perform versus the 777F. Will it be able to deliver larger 747 size loads with lean 777 style fuel flows? Will there be a market for these kind of loads? The future will tell...
