"There’s no denying that while the Airbus A380 is the best plane in the sky in terms of passenger comfort"
Debatable for sure. In business class, in particular, I know of lots of complaints due to the oversize business cabin and impersonal service that often results. That's among other complaints like a chaotic boarding process or that often 380's consolidate away a frequency that many passengers preferred. Also the A380 upper deck is narrower than a 777 and much narrower than a 747 main deck. Given the same seating layout (which is really only going to happen in first or business class), the Boeings would be more spacious.
"The 747-8 was in theory a breath of fresh air for the 747 “line,” though in practice it has been a complete flop."
I'd like to see some numbers to support this.
Given that it's not a completely new plane, only a re-design and upgrade, and that they already have 120 orders, I would be surprised if this wasn't a profitable program for Boeing. As the A380 is not a viable cargo plane, I expect a healthy (though not likely overwhelming) supply of cargo orders to keep rolling in for the 747-8 as older 747's continue to be retired in the coming years.