What do you think of this argument for God?

[Sal]

I heard an argument like this:

1. God is the greatest possible being.

This is just semantics.

2. God is a necessary being, which means that God exists in every possible world (If God exists). 

Non Sequitur.

3. If God exists in one possible world, God must logically exist in every possible world. 

wat

4. Since God is the greatest possible being, it follows that every aspect of God (being possible) exists in some possible world.

Even if the 3 preceding assumptions are given, this is the same as saying that something existing at A also must exist at B, with no further information.

5. Therefore, God exists (in all possible worlds, including ours).

I actually just structured the premises this way myself but is the same idea as an argument I heard before. 

What do you think of it?

I think it's bollocks and semantical toying.