I'm not sure Jacob "created" the smoke monster as such, it seems to me it gave it a vessel to use to manifest itself outside its "prison". It got out by invading something from without the light, MIB's body.

I think the full nature/origin of the smoke monster is still up in the air. The mother seemed to know very well what would happen if someone went in the Light, so it could have happened before, but the Guardian or someone else managed to force the Smoke Monster back into his prison, and then Jacob released it again.

The final answer may come only in the finale, if "re capturing" Smocke is what the new Guardian will have to do. It sounds like Jacob was unable to do that for some reason, if it's feasible anyway. They also have not given us "the rules". The monster is unleashed, but we still have no idea how and if Jacob managed to make it obey his rules later, and how the monster is confined to the island (though it does seem to me the monster can appear as "ghosts" outside the Island, like Jacob can apparently leave the island. He couldn't in yesterday's episode - so there's more developments in this backstory to tell/explain).

Or you may be right: the Evil One was never released on the island before, and Jacob was the first guardian to fail.

There are answers about the Light and the evil within that they haven't given us yet. From what he told Richard, Jacob has discovered a lot more about the Island's nature and purpose than he knew in that episode.

The mythological influence still seems mostly Persian/Zoroastrian. Evil was hidden in the light but was allowed to touch men and creation, like a disease. It needs to be fought by serving the light.

If the forces on the island are truly the fundamental forces (Good/God and Evil), then the island was no primeval garden in Jacob's day and evil already touched the world, and that would speak of Evil having been unleashed then captured before.

The four-toed statue is a strong clue that the Island has a past going way beyond Jacob's days, into purely "mythological times" (ie: contradicting RW history/prehistory) it seems. In the show's mythology, it may be the origin of the world.