Credit card issuers have downgraded the value of cash rewards over the past couple of years, while improving their merchandise and shopping voucher offers.Research company Canstar reviewed 145 reward programs offered by 43 providers and found that, among non-flight reward options, merchandise represented the best value.According to Canstar, a cardholder spending A$24,000 a year on a credit card would qualify for a merchandise reward worth an average of $199.98. The average value of merchandise rewards, per $24,000 of annual spend, has increased from $171.27 since 2011.The value of shopping voucher rewards, per $24,000 of annual spend, has increased from $151.73 to $173 over the same period.The value of cash rewards has fallen from $143.30 to $124.07 over the same period.Canstar said that, if the same cardholder put their points into a frequent flyer program, they would need 16,000 points for a flight from Sydney to Brisbane on Qantas and 13,800 points to make the same journey on Virgin.The cardholder would need 128,000 points for a flight from Sydney to London on Qantas and 125,000 points to make the same journey on Virgin (all calculations are based on ticket prices in March).Canstar said there had been very little change in flight rewards over the past few years.For programs offering cash, merchandise and vouchers (assuming an annual spend of $24,000), Canstar awarded five-star ratings to the American Express David Jones Card, ANZ Rewards Platinum, Coles Reward MasterCard and the Myer Visa Card.For frequent flyer programs ($24,000 spend), Canstar gave five-star ratings to the American Express David Jones Card, American Express David Jones Platinum, American Express Qantas Discovery, American Express Velocity Escape, ANZ Rewards Platinum, NAB Qantas Rewards, NAB Velocity Rewards, NAB Velocity Rewards Premium and Westpac Earth.