One way of countering the argument would be to deny the premise and say that you do not have a perfect idea of God. Rather, you have only an approximation of that perfect idea. Since our idea of God would then be imperfect, it would not require a perfect cause and the conclusion wouldn't follow.
The first argument for God is in Meditation 3, when Descartes examines the nature of God. Descartes deduces that God would only come from three sources of information: senses or experience, imagination, or an innate idea. God can not come from experiences because there are limitations to our experiences and since God is perfect and limitless, we can not experience him. He can not come from our imagination because our imagination comes from all of our experiences, and since our experiences are bound, as is our imagination. Therefore the idea of God must be innate, we must be born with the idea. And the only possible source of the idea of God can only come from God himself.

Now, in the Third Meditation, Descartes hopes to deduce and prove the existence of something greater than himself—in this case, God. In order to do so, Descartes establishes two different arguments for the possible existence of God. In his first attempt, known as the “Causal Argument”, he examines what exactly is necessary for something to be the cause of its own effect; his theories on the origin and conception of ideas are used to try and not only proving that God exists, but that he is the cause of himself. Something in this logic does not sit well with this writer: namely the belief that “no idea is in and of itself truer and has less of a basis for being suspected of falsehood” (Med III, paragraph 25). By stating that an idea cannot be conceived of by any being less than itself, Descartes limits the potential of the human mind and seemingly creates a circle of doubt and questioning; it is this circle which I challenge: the reasoning of the causal argument and the beliefs on conception of ideas can be called into question. First, I shall examine and define the terms which Descartes uses to create the base foundation for the causal argument and, second, I shall attempt to challenge the “Causal Argument” by examining the logic of the Cartesian Circle of Doubt within the definition of ideas.
The main point, or power, of the causal argument lies in Descartes assertion that whatever is contained objectively in an idea must be contained either formally or eminently in the cause of that idea. In layman’s terms: one cannot create the idea or truly conceive of anything that is greater than his or herself. Hence, Descartes states, it perfectly plausible that God must exist by that count as “[man] should not, however, have the idea of an infinite substance, seeing [he is] a finite being, unless it were given [him] by some substance in reality infinite” (III, 23), aka: God. This is the first place in which I am displeased with Descartes argument and assertions.

Descartes second argument can be viewed as a traditional version of the Cosmological argument for God's existence. Descartes' existence either came form himself, his parents, from another source less perfect than God, or God. He rejects the idea of himself causing his own creation. He concludes, "But were I myself the author of my being, I should doubt nothing and I should desire nothing, and finally no perfection would be lacking to me; for I should have bestowed on myself every perfection of which I possessed and idea and should thus be a God."
Although his parents may be the cause of his body, they are not the cause of his thinking existence. If they were to be the cause of his existence, they would have just as much reality as Descartes would. Descartes supposes that his parents are not self-creative and concludes that "although all that I believed respecting them be true, it does not, nevertheless, follow that I am conserved by them, or even that I was produced by them, in so far as I am a thinking being. All that, at the most, they contributed to my origin was the giving of certain dispositions (modifications) to the matter in which I have hitherto judged that I or my mind, which is what alone I now consider to be myself, is inclosed; and thus there can here be no difficulty with respect to them, and it is absolutely necessary to conclude from this alone that I am, and possess the idea of a being absolutely perfect, that is, of God, that his existence is most clearly demonstrated."
A further suggestion is that Descartes was caused by a finite cause less perfect than God. He responds noting that this finite cause would have to possess the idea of infinite perfection as well; therefore we need to inquire into its cause as well. "All other possible candidates have been eliminated as a source for his existence, God alone remains; and, given the truth of the principle that whatever exists has a cause, it follows, Descartes declares, that God exists we must of necessity conclude from the fact alone that I exist, or that the idea of a supremely perfect В– that is of God В– is in me, that the proof of God's existence is grounded in the highest evidence" Descartes concludes that God must be the cause of him, and that God innately implanted the idea of infinite perfection in him.
Descartes second argument for proving God's existence is very straightforward. He has four possibilities that created his existence. Through process of elimination he is left with God being his creator.