Yes, but the point is that even Alexander the Great was never literally referred to as "ruler", even when he was basically ruling over a large chunk of the "known world".
Arguably, the sort of figures most likely to be referred to as "Leader" or "Ruler" tend to be the most autocratic tyrants. Whether we're talking about the "Great Leader" of North Korea or the "Leader" (Duce) of facist Italy, or the connotations of supreme rulership that tend to be tied to the "Emperor" title in Asian cultures like China or Japan, there's sort of a line to be drawn by someone who simply leads men into battle or in peace time, and someone who holds a position that essentially represents the incarnation of divine rulership (and whose title literally means "ruler" in their language).
I would imagine being a "Leader" would be the same as a "King" in which they have skills associated with the title.