We're Southwest fans. However, we did have a pretty good experience flying Delta (and eventually Air France, its partner) from Phoenix to Tunis this year. The overseas flight had decent food and lots of it, as much in-seat entertainment as you could want, and friendly service. We flew coach and the seats were no more uncomfortable than those on any other airline. I know that is not saying much, but it is something.
As for airports, in Florida, Fort Lauderdale, which years ago was welcoming, is overly busy and under construction and dumpy. Miami is a mess. Orlando still offers a welcoming tourist experience. West Palm is smaller and better for it. Tampa was not bad when we flew out of there last year.
Here in Phoenix, Sky Harbor is good now that they have fixed what we thought was the slowest baggage claim service in the world. We do not like Houston/Bush at all. San Diego, with its single runway, is quirky, but I like it a lot. Do not like Boston Logan and over the years, the area around T.F. Green in Rhode Island has turned into a kind of slum. Toronto is a giant ark of a place, cold, impersonal, not fun. We hate Atlanta with a passion, both because we don't find it friendly and because it seems delay-ridden.