I've flown a lot in the past few years, all over the world, and my experience is that the Asian airlines (Cathay Pacific, Singapore Air) offer the best overall service, though they tend to be expensive. Unfortunately, if you're going from the US to the UK, they are generally not an option. I've had reasonably good experiences with Air Canada, Air France, British Airways and Virgin Atlantic. These days, I do my best to steer clear of the American carriers, their service has gone from bad to atrocious lately. It's a shame, the first time I flew over the Atlantic in 1999, I went on American Airlines and was actually impressed. Then I was on an AA domestic flight a few months ago, and it was awful. Makes me sad.