The argument from degree

[Objectivist]

I like your answer.  I've also heard that an even greater being could do all of the things that gods are supposed to do but it could do them while not existing, therefore god does not exist.  

Aquinas' argument is total rationalism or reasoning above facts.  The first cause is existence qua existence.  Where does life come from?  Existence.  Where did the earth come from?  Existence.  Where does consciousness come from?  Existence.  It's existence all the way down.  Where did existence come from then?  Blank out.  There's nowhere for it to come from or go to.

According to Aquinas, the first cause is one and the same as existence. So while I'm sure you mean something quite different from what Aquinas argued for, the wording here isn't too different from what he said.

That said, could you elaborate on what you mean by existence here? It seems to be something concrete here, rather than an abstract.

The concept 'existence' is an abstraction but it references everything that exists so it's the widest of all abstractions.  When I use the concept in this context it is taken to mean existence as such and not any particular existent.  The concept 'existence' means every concrete, its attributes, its actions, its relationships, everything.