It tends to vary by Cruise company & by rank.
For example on Princess if you were allowed to eat in the officers mess it was pretty good. You could order from the passenger menu with the exception of certain items, or you could eat from the buffet trays if you were in a hurry. The crew mess however was buffet trays only so not always the best!
On Regent even for the officers, its all buffet tray food & to be honest is not all that great - although all the other perks of working here far out weigh the downside of the food...
Its a question of balancing up the pro's & con's of whichever company you decide to work for at the end of the day!
Good luck :-)