RC and Celebrity are nicer lines (Celebrity's food is one notch better than RC) and Carnival is way below all the rest. They're the budget cruise line. You can get last minute cruises on their line for a couple hundred bucks.
Disney, I hear, is at the same level as Celebrity.
Been on two lines. Carnival is cheapest price wise, but Carnival’s entertainer/comedians are filthy.
Norwegian has cleaner comedy but the Norwegian ‘freestyle cruisin’ sucks. We waited an hour, no place to sit, or bar, for a dinner table more than once. The assigned/set dinner seating like on Carnival is much better.
All cruise lines are shifting more and more of the expenses to ‘Govt taxes and other fees’ category. You may get a cruise for base price of $150 but the ‘tax and fees’ are over $100 on top of that and the gratuity is another $75.
So real cost is more than double the advertised price.
Note: Govt taxes and other fees are not-mandated costs. There are costs of the cruise line doing business added in there that used to be part of the base price. Like baggage handling, the cost of the third-party staff in the port, etc. And don’t ever try to get an itemization of these bogus fees.