I talked to Plantinga about his ontological argument. He considers it the weakest as well. In his own words, “this is because the conclusion is too close to the premises.”
It's the strongest in my view, because it shows how God is a proof for himself. This is the main reason people don't like it and so have to resort to predicate non-sense in universities and what not, and it's that when you remember God in this greatness/highness/bigness mathematically, there is no room for doubt after, and it's magical the remembrance of God and his proof of existing - by sheer bigness - it just seems to good, but it's mathematically correct. Then it's impossible God is an idea, by definition, he can't be imagined but only seen to exist. I think Plantiga and Craig both don't realize how strong this argument is and hence feel it's too good to be true.
That said I use to throw this moral argument and wondering what you think of it:
If God can create morality from nothing, he can make it whatever he wants.
If he can make whatever he wants, it can be arbitrary.
If it can be arbitrary, it can be deemed moral to forever torture babies for no crime they done in severe torture/pain with no end to it.
It cannot be in any possible world that it's moral to forever torture babies for no crime they done in severe torture/pain with no end to it.
Therefore morality can't be abitrary.
Therefore God can't make it whatever he wants.
Therefore God can't create morality from nothing.
If God can't bring in morality so can't evolution since God can create everything evolution can (structure wise).
Therefore morality exists eternally.
If morality exists eternally, it includes all levels of moral greatness and possible goodness.
The only being that can see ultimate morality is God
Therefore God exists eternally.
This is a longer argument, a little hard to wrap head around, but to me is a sound argument.