I think I honestly have to say easyJet. Obviously there is always the odd bad apple, as I have related occasionally on this board, but overall they are generally excellent, in particular in dealing with the wide demographic spread they have on any given flight (bear in mind most of my trips on EZY have involved Schiphol, so there's a huge spread from stag / hen trips to business parties on-board). I've worked at a fairly high level in service industries before (in both service and managerial capacities, in high-quality hotels) and I admire their general ability to speak to the person(s) they're speaking to, rather than adopt some droid-like, unchanging attitude to all and sundry.
KLM are generally good but I think, as elsewhere with the Dutch, I'm spoilt by their tending to treat me very well since I'm an Englishman who has bothered to learn their language
I've seen too many sloppy or disinterested individuals though to put them level with EZY.
I've quite enjoyed the BMI / BMIBaby experience, although nothing to write home about. I'll not detail the airlines I've disliked, but you can guess at least one of them
