I'll take door # 2:
I exist. My existence must have a cause. The cause must be: a) myself, b) my always having existed, c) my parents, d) something less perfect than God, or e) God
OK, I start having issues here. It seems that only d and e cover the entire universe of possibility, so a, b, and c are already spurious.
Not a. If I had created myself, I would have made myself perfect. If he were perfect he'd be god, by his own rationale; if he could have made himself perfect he would be god, so either way, he's contradicting his own presupposition that god exists but isn't him.
Not b. Continued existence does not follow from present existence. No, but existence can follow from past existence.
Not c. This leads to an infinite regress. Well, no, it doesn't; it goes back to the beginning and then stops.
Not d. The idea of perfection that exists in me cannot have originated from a non-perfect being. And here we have the rub: Whyever not? Therefore, it is an incorrect conclusion that e. God exists.

(hope I make it through the italicizing and unitalicizing. Descartes is meant to be in italics, and me, not.