If you read the section entitled "Gods" (OW60; also the table on OW28) it pretty well summarizes the "best available truths" regarding religeon in DF. You'll notice some equivocating ("It is said"), and some of the material is 'new' to the DFRPG, thus making it a secondary source -- but until Jim reveals more, its what we have.
And what we have is that at the top of the power tree by orders of magnitude is "The Almighty (AKA the Creator, Michael’s Boss)". We also have that "most gods are the first generation scions of angels, demons, or powerful beings of the Nevernever. Some of them are derelict angels—not cast out of Heaven, but just departed on their own." There's a definite distinction made between all of these assorted gods ("Greek, Roman, Norse, Amerindian divinities, African tribal beings, some Australian Aboriginal gods, others in Polynesia and southeast Asia, and about a zillion Hindu ones") and "the Almighty, the “capital G” God, and Jesus Christ".
There is talk about how the little-g gods may vary in power scale due to lack of mortal worship and such, but there is quite definitely a large distinction many between "gods" and "God" in the world of the Dresden Files.
Note that all of the above is discussion of religeon in the Dresden Files, you are free to believe in absolutely anything you want in real life.