We love Celebrity cruise lines and a close second is now Carnival. Watch out for Princess cruises as the food is not up to same standards as Celebrity or Carnival and since eating is an integral part of cruising I cant recommend Princess.
Royal Caribbean used to be good but they have dropped in quality over the last few years so while I wouldnt necessarily avoid them I cant recommend them either.
I havent cruised with NCL so I dont know about them.
Holland America has great food and superior service, but they target an elderly audience and the music, shows and tour excursions reflect that. Good news is you can outrun the people on walkers at the buffet line :1circling