Oh no, here comes Willravel!
Just a few thoughts.
Ontological Argument 1 (pre-Plantinga): While I enjoy the way this looks on paper, god isn't necessarily the greatest being imaginable. 'Great' is subjective and vague, thus I can imagine things that might be greater than god by my standards.
Ontological Argument 2 (Plantinga): Interesting, but when I apply it to something else, it becomes deliciously incorrect. Let's say that I have P, a potato chip that has infinite surface, height, and perfect taste. This is the greatest potato chip ever, ever. P is the greatest potato chip that can exist - existing is greater than not existing, therefore P must have existed (before I ate it).
Plantinga is brilliant, probably a genius, but he is notorious for question begging. He displays a lack of understanding of basic science (stating that earthquakes, weather, and radioactive decay are not subject to natural laws).
http://www.arn.org/docs/odesign/od181/methnat181.htm
http://www.arn.org/docs/odesign/od182/methnat182.htm
At the end of the day, he's just trying to cover for the use of supernatural explanations of scientific phenomena.