The 'old gods' are clearly not real in the sense that they were considered to be a collection of nature deities, as ADWD indicates all they are is the collective memories of greenseers 'plugged into' weirwoods (like an arboreal version of THE MATRIX) over the millennia which endure after the greenseers' deaths. So the old gods have a real and comprehensible underpinning to them, but not a divine one.

R'hllor and the Great Other appear to be divine personalities assigned to sources of power that are real and can be tapped by humans under certain circumstances. I don't think either exists as a literal sentient and divine being. The Drowned God and the Seven don't appear to even have that kind of power going for them, and are purely mythical (and that's reinforced when we're told the Rhoynar taught the Andals how to smelt iron, not the Smith as the septons claim).