Of course, it would depend upon an individual/s taste, but look towards the luxury lines as having the best food. I would say Radisson, Silversea and Crystal would be the top choices ( of the major cruise lines, that is).
"Best food" is such a subjective term that you are likely to get many different answers. Depending on individual experiences on a particular week on a particular ship, as well as individual tastes opinions are going to vary drastically. Also, those people who are willing to pay an additional fee and choose to dine in the alternative or specialty restaurants are often served a much better quality meal than what is served in the main dining room. But, I have to agree with Tom, if you are looking for the most consistent level of excellent cuisine than the luxury lines will more than likely deliver.
In response to your question, while it is true you usually get better cuisine on a better cruise line, I take exception. Royal Carib has my favorite dining selections, but I was not impressed with the alternative dining. Carnival, I felt was very below par, yet, on the Conquest, alternative dining was excellant. A trip on Celebrity Mercury, with Tom, this November, did not meet my expectations. I expected better, as Celebrity touts better dining. On QE2, post 911, our Queens Grill cruise was as expected, perhaps better than expected.
Welcome to Cruise-chat. Actually your response supports my premise, that "Best Food" is very subjective and our individual experiences and preferences obviously impact our opinion. I too, as a rule, find Royal Caribbean cuisine in the main dining room to cater to my personal taste. On my most recent cruise onboard the Brilliance, however, I found the food at both specialty restaurants to be outstanding (particularly Portofino). But, by the same token, I was extremely disappointed in the specialty restaurant aboard the Celebrity Infinity a few months ago. And so the debate lives on!
Not having cruised on any of the Luxury Lines or having eaten in any speciality restaurants my comments are limited to main restaurant dining.
My wife and I rate our experience on Celebrity the best by far. After that it is a close call between Holland America and Carnival. Royal Caribbean and Princess rated lowest of our recent cruises by the simple test of how many times we had to resort to the old standbys of steak, salmon or chicken because we fancied none of the listed entrees.
Cunard QE2 1984 & 1990
Carnival Fantasy 2001, Inspiration 2003, Glory 2005,
Celebrity Horizon 2004, Galaxy 2005, Summit 2006, HAL Zuiderdam 2004, Veendam 2005
Princess Star 2003, Sun 2004
P&O Oceana 2004
RCCL Nordic Empress 2002
Regal Empress 2002
RCCL Legend of the Seas Apr 2006
Saga Ruby June 2006
P&O Arcadia July 2006
Carnival Miracle Oct 2006
RCCL Navigator Apr 2007
P&O Aurora Sep 2007
QM2 Sep 2007
Sapphire Princess Apr 2008