Discussions of which airline is best is meaningless as there is not a lot of difference in in-seat quality between most western airlines.
What counts for me is how the airline reacts when things go wrong. So for example, how will the airline react if the aircraft goes tech? How quickly are they likely to get a replacement? Will they quickly and efficiently book you into a hotel, or onto a rival airline? Also, if I am going to a destination with frequent bad weather, how likely is the crew/aircraft to have full CatIII ratings? These are the sort of things that can really ruin a holiday if the airline is hopeless at sorting out an unforeseen problem.
I generally thus avoid any airline that is not profitable. Thus I no longer fly with Alitalia (having been the victim of one of their chaotic episodes). An unprofitable airline is likely to be cutting corners wherever it can - so do not have standby aircraft and crews, often do not employ competent expat local managers.
I also avoid any airline which has to operate in a culture of corruption/nepotism, because it is very unlikely to be accountable to its passengers if things go wrong - for example try getting your money back from an African airline if they cancel a flight .... good luck!