For me its a straight fight between BA and SQ and nothing really comes close to the feeling that they give me when travelling and that is irrespective of class.
I do fly a tremendous amount with Etihad and they have a pretty good product but it lacks substance. In addition to that they have no idea how to deal with high mileage frequent flyers, to them you are cattle just like everyone else. I do not expect special treatment but they lack the touch and sensitivity of my two favourites.
One to avoid for me is Qatar airways, every part of the travel process is fraught with problems due to incompetent staff on the ground. no issues with cabin crew at all though
Easy jet always works for me as well so i fly them when on short haul in Europe which is once in a blue moon