Well, after 35 years of business travel and 94 countries later, in my experience ....
- American carriers (all) - impersonal, cold and unfriendly no matter how much you try, best avoided,
- new & expanding Middle East carriers -usually good, but often lack of experienced cabin crew shows through, you kind of have to grin and bear it if it goes wrong because they're too nice to make a fuss,
- Lufthansa and Swiss, personally, my favourites - consistency and efficiency are the key,
BA - Jekyll and Hyde; when they're good they're outstanding, when they're bad they just don't give a damn. Overall though, average. Can't forget tent city in the T4 car park a few years back, although that wasn't the crews' fault
Qantas - sometimes make you feel like you've got a nasty disease - I never got over being served by CC wearing plastic gloves during a time of heightened HIV publicity a few years back.
Best recent experience - Jet Airways to Mumbai - almost perfect !
Many others, but those are the outstanding ones.