Well, hence the confusion about Spinoza's God. It's not really ontologically distinct for him, since his God 'is' the universe. (His God is also just mental-stuff, but Spinoza was an idealist, so to him all stuff was mental-stuff.)
Now, Spinoza's might not count as a 'Matrix Lord' since he denies that God 'chooses' anything in our sense (he holds to a very strong version of the Principle of Sufficient Reason) so it's not like God is 'running' the simulation, as it were: God just is the simulation according to Spinoza.
Likewise, most theistic philosophers are comitted to God being omniscient, omnipotent, and (usually) omnibenevolent. But some put that in 'absolute' terms while some put it in terms of this world: omnipotent regarding this world, etc. For the latter group, there is no clear philosophical dilemma in saying that a Matrix Lord counts as God, especially if that Matrix Lord is also the "First Cause."
In fact, assuming that such a Matrix Lord exists, most theistic philosophers would be required to say it counts as God.
Despite being (IMO) a philosophy blog, many Less Wrongers tend to disparage mainstream philosophy and emphasize the divergence between our beliefs and theirs. But, how different are we really? My intention with this post is to quantify this difference.
The questions I will post as comments to this article are from the 2009 PhilPapers Survey. If you answer "other" on any of the questions, then please reply to that comment in order to elaborate your answer. Later, I'll post another article comparing the answers I obtain from Less Wrongers with those given by the professional philosophers. This should give us some indication about the differences in belief between Less Wrong and mainstream philosophy.
Glossary
analytic-synthetic distinction, A-theory and B-theory, atheism, compatibilism, consequentialism, contextualism, correspondence theory of truth, deontology, egalitarianism, empiricism, Humeanism, libertarianism, mental content externalism, moral realism, moral motivation internalism and externalism, naturalism, nominalism, Newcomb's problem, physicalism, Platonism, rationalism, relativism, scientific realism, trolley problem, theism, virtue ethics
Note
Thanks pragmatist, for attaching short (mostly accurate) descriptions of the philosophical positions under the poll comments.
Post Script
The polls stopped rendering correctly after the migration to LW 2.0, but the raw data can be found in this repo.