My "comped" four night stay at Mandalay Bay is gonna cost me $167.80.
If you're willing to play greens/low blacks you can usually get an "okay" game of 3:2 blackjack on a cruise ship. Then again this is if you get comped a cruise (which I think is what you're looking for - a way to get comped a vacation?). You could always call a cruise line, ask to speak to their casino, then ask for a host and repeat this question to them (aka will you comp me if I'm playing black action each day?).
It's been my experience that the rules for BJ on cruise ships are horrible so I wouldn't count on that. Also, if you want to try to get a free cruise with the line you need to have a history with them with the ships's casino department."I should have bet black." - Winston Churchill .