Celebrity of course offers higher standards in this department. No doubts about it.
There are other variables to this equation. Like number of ships offered from Northeast (Boston, Bayonne, Baltimore) for example and more.
However restaurants on RCI while not perfect (X food is better), but good enough.
I'd prefer existing ambiance remaining. Not too formal, not too riff raff, Nice balance.
Every line we sailed with (starting 2003)
Celebrity - 7 times
Princess - 7 times
Holland America - 2 times
NCL - 9 times
MSC - 2 times
Cunard - 1 time
except for Carnival (3 times) had something better than RCI, but overall RCI offers the best value and variety for us.