Personally, I agree with Ronnie about Carnival. But then again, as I always say, what one person loves another will hate.
We've never had a bad experience with Carnival and have enjoyed all our cruises with them, but we definitely prefer other cruise lines. But we're older and we appreciate the finer things in life, especially good food and good service. This is why our all-time favorite is Celebrity. But because it attracts an older crowd and is a bit too sedate for some, younger people don't particularly care for them because there's not alot of nightlife. Their food is excellent and their newer ships (the Solstice-class) are wonderful.
Younger folks tend to prefer RCCL because of all the amenities, especially on their new ships like the Oasis-class ships. However, I have been somewhat disappointed in the quality of their food lately in the main dining rooms. Not up to the quality it had been a few years ago.
Perhaps this is why if we're doing a group cruise with family and friends, we really like Princess. Food is better than RCCL, but there aren't quite as many amenities.
Food is very subjective - sort of like McDonalds vs Burger King; some like one over the other, some like both, and some like neither.
And this is the best part about cruising; there's something out there for everyone and the fun is in trying them all until you find the best one for you.