Vivec followed the fifth walking way(The other two tribunal never achieved CHIM from what I recall). If you want a "God" in elder scrolls, the closest thing is the dreamer. The Scarab that transforms into the New Man also seems to be a similar figure, though there's no records of anyone successfully becoming this(Save for the fifth era loveletter).
While I'm not very brushed up on the Loveletter, I do know that the Scarab is Lorkhan. As he is directly connected and cause of Aedra turning into humans, I can only assume it has to do with ascension of his people into the a sort of new godhood. A new plane of existance, if you will.
The "dreamer", by which I assume you're talking about the God-Head and not Dagoth Ur, is very complicated. I mean, as he is in a way the supreme creator, and in a way is also is the entire universe in himself, he is somewhat like a god, or "the" God. Then again, he is completely extraneous to the beings of the universe, and is irrelevant and unaware almost to the point of being non-sapient.
Personally, I have also always enjoyed the thought of the God-Head as an extended metaphor for the player himself.
What about Sithis?
Sithis is more like force of nature than a deity. And anti-force of nature, even. Worshipping him is as useful as worshipping gravity, or temperature.
Ninja'd by Cecil, but still.