The fine tuning argument suggests that if certain universal constants were any different, life would not have arisen.
Since this is better explained by a God who wanted life to arise, it is taken as evidence of God.
However, there are many things in the universe that would be better explained by God. In fact, everything in the universe can be better explained by a God by simply building that thing as a preference into the God hypothesis.
For example, John in some city played poker and got a Royal flush as a hand. The probability of him getting the Royal flush is indescribably low. This is better explained by a God who simply wanted John to get a royal flush at that moment.
What is the difference in logic between these arguments? I fail to see any. The reason the second argument fails is because it tells you nothing about whether or not God exists. A certain property of the universe occurring that may be valuable to a particular kind of agent says nothing about whether that kind of agent actually exists, unless we have independent reasons to think that agent already does. Does this mean that the fine-tuning argument, by itself at least, rest upon a fallacy?