Most cruise lines (especially the ones listed on this page) requires you to have a co-branded cruise line credit card to earn rewards. For example, you need to own the Barclays Carnival FunPoints Mastercard in order to earn rewards with Carnival Cruise Line or own the NCL Mastercard to earn WorldPoints with Norwegian. Cruise line rewards points will typically have the best value when redeemed for high costing cruises. If you don't spend a lot directly with cruise lines and don't plan on redeeming your points for expensive cruises, a cruise line credit card will probably not be the best option for earning rewards.
You can click on any of the cards listed on this page to learn more about them, calculate total rewards based on spend, and compare them against top rewards cards featured on the site.