that's not my experience, unless you dump a seat per row, you simply cannot get the same space per seat, name me a narrow-bodied jet with a layout that's got the same or better seat width as the A380.
Well the 777X cabin is
wider than the A380 upper deck cabin where most F and J seats are typically configured.
A380 upper deck cabin width: 5.92m. 777X: 5.97m. 777-200 and -300: 5.87m.
Even on the 787, the slightly narrower cabin doesn't make a difference in F. BA has the same seating config (1-2-1) on both the 787 and A380. The difference is you have 8 seats in the 787 but they cram 14 on the A380. So the service on the 787 is actually a bit better and feels more exclusive.
That is (mostly) true of flights of 6 hours or less. Above 6 hours it starts making a difference. Above 10 hours it starts making a big difference. Above 12 hours and it makes a difference to almost everyone, including the flight crew who are theoretically the most well adapted and least sensitive.
That might be true if you're comparing 6000ft vs 8000ft. But on all aircraft we're talking about in this thread (A350, A380, 787, 777X, 747-400) the design target cabin pressure will all be ~ 6000ft +/- 500, barely noticeable difference for pax, and if anything the A380 will be the worse of the bunch.