God Is Love, and from here is where all Gods actions originate.
In short, if the question is: why does God create? then the answer can't contain the word "creation" nor in any way imply it. Because if you say that God created due to His love for creation, then all you're doing is forcing me to re-word my question to: why does God love creation? Usually, in my experience, the answer from most theists (often Christians) boils down to "well, we don't really know." But I like to take this issue a step further. Even if we do not know exactly why God creates, my next question would be: why MIGHT God create? In other words, what is a possible reason a self-sufficient, eternally blissful being would create a world of fleeting forms?