Yes and no. They will typically have the same menus and ship services (some newer/larger ships may have some additional services); but the actual food quality and service can vary significantly ship to ship. RCCL does what they can to keep things at a consistant high quality, but it will still come down to how that individual ship is run/managed.
Carnival Breeze - Jan 2013
Carnival Conquest - 2011, Oasis of the Seas B2B - 2011, Carnival Conquest 2010, Carnival Ecstasy - 2010,
Carnival Conquest - 2009, Carnival Ecstasy - 2009, Brilliance of the Seas (Med) - 2008,
Carnival Miracle - 2007, Carnival Conquest - 2006, Rhapsody of the Seas - 2005, Vision of the Seas - 2003,
Rhapsody of the Seas - 2001, Carnival Inspiration - 2000, Carnival Jubilee - 1999