I have to agree about LAX being the worst airport (at least in my own limited experience). There really are no redeeming features about the physical environment. For the best airport, that is difficult. I quite enjoy SYD, Changi is great. I like the groovy 50's/60's architecture of Dulles main building, although the buses are a pain. SFO is a disaster zone (at least when I was there three weeks ago). OAK is pretty depressing. Narita, when I was there years ago, was pretty bad.
For airlines, that is difficult since they all can vary quite a bit in my own experience. I have had some excellent service on American between LAX-IAD, which was a pleasant surprise. Ansett were always pretty good. Personally I find the 'peppy' attitude of some of the low cost airlines a bit grating, but maybe that's just me. I think I will leave this question to more experienced flyers than myself.