Malls are outperforming every other property type after years in which their decline appeared inevitable. Values rose 13% over the past year, more than double the gains across the overall commercial real-estate market. Resilient consumer spending and strategic shifts toward luxury retail, dining and entertainment have helped bring shoppers back. Simon Property, the U.S.'s largest mall owner, is hitting record stock highs as investors reassess the sector's long-term staying power.