Here are my 2 cents...
Virgin Atlantic:
Virgin Atlantic was just ok (nice stewardess, good entertainment system) but SUPER SUPER SMALL AND UNCOMFORTABLE SEATS.
I mean, tiny. I'm 5'1 and I was cramped. The seats are "trendy" and they curve up on the edges. Horrible design. Plus in economy it was that gross cloth seating so it was smelly. Ugh.
On the way home the Virgin Atlantic crew were very, uh, curt. The manners were curt and I fell like I was being reprimanded every time I asked for something. Our entertainment system frizzed out on the flight home so there was nothing to watch. The food made me nauseaus (no joke). We were served some kind of fish jelly (or maybe it was fake pate). Ughh.
British Airways:
I thought I'd hate BA, but I flew them last time and the service was good. The planes were bigger and it was kind of like a cattle call but the seats were comfortable. Service was friendly and generally acceptable. Bathrooms were kept clean the entire flight (which wasn't true for AA). Terminal 5 at LHR is amazing. If you connect out of there, you won't be bored.
Lufthansha:
By chance we got that famous $200 (incl tax) airfare to Rome in 2005 while KLM was going through bankruptcy reorganization. Lufthansa flights were comfortable, service adequate but the connection times were horrible and they hub out of Minneapolis and that is a sad airport. Our connection out of AMS was delayed by 5 hours so we sat in that airport for 11 hours.
After that, I consider them unreliable.
Air France: Loved them! Good service, acceptable food. Our luggage took some time coming out but hey, it wasn't that bad.
For our Med cruise next year, we are flying BA going and UA coming back.
Air Berlin codeshares with AA, so make sure if you choose AA you're not actually buying an Air Berlin flight (if you don't choose them). They tend to have long layovers in MUC or BER.
HTH.