I don't think the Metrons really qualified as "gods," but rather people whose technology was just a bit more advanced than the Federation's. What did they have really? The ability to bring two starships to a halt in space would seem to be the big one, other than that the Metrons had a long range transporter.
The caretaker would also fall under advanced technology as well. He possess no natural abilities that were "god-like," just machines.
Apollo did have a unusual organ in his chest, the machine in the temple boosted his power, but the impression I received was that he could manifest god-like powers on his own, maybe at lesser levels.
Trelane had a machine too, but didn't seem to need it, so god-like.
The Dowd, Q, Prophets, Organiains all seem to meet the definition.