* Hoplite: This refers specifically to a heavily armed Greek infantryman of the classical era. It's probably the closest single word equivalent.
* Warrior: This is a perfectly acceptable general term, though less specific to the Greek context.
* Soldier: A more general term still, but applicable.
The best choice depends on the situation. If you need to be precise about the historical period and equipment, "hoplite" is best. Otherwise, "warrior" or "soldier" will work.