
I feel that Mexican cuisine gives you the greatest diversity of different foods due to the mixture of many very different cultures old world and new world. You have access to foods all the way from the north of Mexico to the Yucatán, and a variety of cheese, meat, and plant-based dishes. You get dishes culturally influenced by indigenous cultures, Spain, Lebanon, Italy, Germany, etc. Gives you the most options.
I mean China and India are more culturally diverse places but don’t draw from cuisine styles from around the world as much. Because of Mexico’s history of immigration there are regional cuisines with influence from the Middle East, Asia, Europe, Africa, and the Americas. Like you won’t have many cheese dishes in China or China.
I still think Mexico might be better for diversity but recognize I have only experienced a small subset of Chinese cuisine (mostly from the southern coast) and an even smaller subset of Indian food. I have a better understanding of the variety of the regional cuisines of Mexico so it still feels more diverse to me but I recognize partly that could be due to me not having many experiences with regional varieties of Chinese and Indian food