If there is a Flying Spaghetti Monster in a possible world then he is possible. If there is a Magic Pen in a possible world then it is possible. This argument is ridiculous and has been refuted. It can be used for anything, there's no reason why an Almighty God is more logically possible than a Flying Spaghetti Monster or a Magic Pen.
Just because an idea is logically consistent with the world as we know it does not mean that it is true. Time and time again, the one has been misappropriated for the other. The various philosophers at different times have always worked from assumptions that guarantee that certain constructs of the mind are reflected in the world. There is no reason this should be the case, or that those constructs would correspond to god if it were. Also, all forms of the ontological argument give such a vague definition of god that I would hardly use it as a basis on which to claim the existence of the Abrahamic god or any other particular god, more of a metaphysical entity with great power or essential goodness. These properties are not exclusive to the Abrahamic religions. Much more detail would be needed before any kind of ontological argument could prove the existence of a god with any specific properties.