I have been on Celebrity, Carnival and Royal Caribbean.
Food on Carnival is up with the best I think in the main dining room. Carnival also has pizza 24 hrs a day. I like Celebrity mostly because of the cabins. Royal caribbian food was not any better than Carnival in the Dining room
Carnival ships sailed- the old Carnivale, Paradise, and Holiday
Celebrity-- Milennium, Infinity,Constellation, Summit, and Horizon.
RCI- Monarch of Seas, Splendour of Seas
Now I am not mentioning the speciality restaurants on the Celebrity ships. Nothing can be as good as that, but the main dining room on Celebrity is not any better than on Carnival at least as of last July.