Many people did not like him because of his tactics, but he spread Greek culture around the world and helped the world modernize and become more global and more interested in trade and culture between nations. However, most experts agree that Alexander was one of the greatest leaders ever. The Columbia Encyclopedia notes, "Incontestably, he was one of the greatest generals of all time and one of the most powerful personalities of antiquity. He influenced the spread of Hellenism throughout the Middle East and into Asia, establishing city-states modeled on Greek institutions that flourished long after his death" ("Alexander...

He was a great general and a great leader, and he was the first person to really encourage a global culture. Our world would be very different if Alexander had not ruled and won so many conquests.
References

Alexander the Great." The Columbia Encyclopedia. 6th ed. 2004.

Holt, Frank L. Alexander the Great and the Mystery of the Elephant Medallions. Berkeley, CA: University of California Press, 2003.

Untereker, Jed, Kossuth, James, and Kelsey, Bill. "The Great Homepage of Alexander." Williams College. 1996. 29 Sept. 2005. http://wso.williams.edu/~junterek/