Sorry, but it's you that is comparing apples and pears !!
The EK B777-300's do have 42 'business' class seats - but they are 7 abreast 'business class'. In the REAL SQ business class they are 4 abreast - like on the A380 - the same seats in fact.
The EK B777-300's have cattle class seating in economy - 10 abreast !!
Sure if you configure the a/c like this you can get 360 seats in it. If you configure the A380 in the same way - 6 abreast business and 11 abreast in economy you will easily get 600 seats in it. And it WILL burn less fuel per pax than the B777-300.
FACT