I seem to recall that the whole "God of Fire" thing was a discredited (or at least unsubstantiated) theory based on a supposed etymological link between the name "Loki" and the word "låga"/"Lohe" ("flame" in Swedish/German, respectively), while in fact it's more likely to have something to do with a word meaning "sky".
In any case, Loki was never worshipped, so he was not a god in the sense used by scholars of comparative religion.