The following is from Compellingtruth.org:
Since that time, many atheists have used Henderson's argument, asserting that belief in the God of the Bible is no more rational than belief in the Flying Spaghetti Monster. However, the comparison of God to the Flying Spaghetti Monster suffers from a number of logical and practical faults.
First, it commits the logical fallacy of faulty analogy. While analogies can be useful in arguments, not all analogies are created equal. A faulty analogy assumes that, because two unlike things may be similar in one respect, they will automatically be similar in other respects. It assumes connections that just aren't there. The creator of a faulty analogy is saying, in essence, "Accept my argument because of these superficial similarities between what you are proposing and my fictitious comparator."
A 30 Second Argument for God