Puerto Iguazú eats well for a small tourist town. Argentine staples are reliably available — parrillas for asado, empanadas, milanesas — alongside fresh river fish from the Paraná that you will not find elsewhere in Argentina. The town caters competently to a constant stream of visitors without ever feeling like it is coasting on captive custom.
Better restaurants are concentrated on Avenida Córdoba and the streets near the bus terminal. Prices are reasonable by Argentine standards even accounting for the tourist economy, and the wine is cheap and drinkable.