I believe that this 'string' of postings proves that the quality of cruies varies not only form cruise line to cruise line, and ship to ship, to individual sailings of a particular ship...
I have been on Celebrity 5, or 6, times and have loved each and every cruise. I have only been on Princess once, but loved that cruise also.
I have only sailed on HAL once, and Royal Caribbean 4 times, and did not enjoy any of those cruises, except for one on RCCI. Wasn't thrilled with Costa either.
I guess it boils down to what voyage you're on, and your personal tastes.