Well, if we are basing this on the Western concepts of god (Judeo-Christian, Classical Greek, Norse Mythology etc...) No, he did not, but to be fair, no villain really achieves god-hood in the FF series since all of them were eventually defeated by the very mortal heroes.

Exdeath is probably the only one who was the closest to being a god-like being for the sole fact that he does pretty much destroy all existence with the Void (including himself) and its only with the intervention of the Crystals that the world is made right. The Cloud of Darkness also falls into this category but I feel Its existence is different as the CoD is more like a "force of nature" that only truly acts when certain conditions are met. The CoD is not destroyed cause it really can't be destroyed yet its power is not infinite as the crystals have the power to hold it back.

In the end, Sephiroth is like Kefka or Ultemacia. He transcends his normal existence becoming something more than human but lacks the fundamental qualities that theologians and philosophers would attribute to a god-like being.

Oddly enough, the traditional Crystals are the closest thing to a god to exist in the FF mythos, though they are based more on an eastern concept of god.