Maize was the most important food in the Aztec diet. It was so important that their whole society revolved around the production and consumption of maize. Apart from that, their diets were largely plant-based, with a little meat. Even their human sacrifice and cannibalism, which could technically be included as part of their diet, revolved around maize.
It was believed that regular human sacrifices were necessary to keep the land fertile and producing the grain that supported their lives and livelihoods. Even today, maize (which most English speakers call corn or sweet corn) is one of the most important crops grown in the Americas. We rely on it to feed livestock, sweeten our food and drink in the form of high-fructose corn syrup, and of course, to eat on the cob on the Fourth of July and other summer holidays.
This is one of the biggest ways that the ancient American civilizations, including the Aztecs, affect modern life, not only in the Americas but in the whole rest of the world as well. In one form or another, maize has made its way into just about every major world civilization.