I think this question is easy to answer. Another question is, why do we remember our loved ones? This means Alexander the Great was loved by his people. He was a true leader, one who fought to achieve a purpose. He never let his people down, and he fought most of his battles with them.
Alexander really changed the ancient world. Alexander was a strong person who fought across different continents like Asia, Africa, and Europe in a bid to conquer the known world. His motive to achieve this was not a selfish one. He wanted a world where people would see one another as one, a world that would share the same cultural values.
Although he had the tendency to become a tyrant, he wasn't described as a tyrant. He demonstrated this when he defeated king Porus but still spared him. He was a true leader, and he led his people with great understanding.