To many if not most biologists, the selfish gene approach is the best idea anyone ever came up with for explaining altruism in the animal kingdom. The only significant rival explanation, group selectionism, is extremely controversial by comparison. The issue is not yet settled. Faust
For biologists the gene is the only hammer they have to bang on things with. Dawkins was a biologist who established his credibility by showing how a gene for distinguishing brighter from darker areas in the environment as an example could have survival value and drive the evolution of complex visual structures collectively known as eyes. He was necessarily working on individual members of the phyla he was studying. As it became necessary to study more complex traits like altruism the gene hammer became the wrong tool and group selection became an alternative for social animals which are a relatively recent evolutionary development. I suspect the two theories are not rivals, but are different tools for investigating different evolutionary structures.
The meme theory, still in its scientific infancy (it's developer isn't even dead yet) may well be the tool needed for studying group selection, as social animals must have a non-genetic behavioral modification adaptation for survival as a group. Group selection works in relatively few generations which make biologists very uncomfortable. Predatory pack wolves evolved extremely quickly into a larger social structure of follower wolves and eventually dogs (and a smaller individual social organization coyotes etc.) with essentially no genetic adaptation. Dogs, wolves, and coyotes can crossbreed with viable offspring, although the strong social differences make crossbreeding unlikely in normal environmental conditions.
The God meme has been extremely powerful in group selection at least for predatory human groups. While it may not prove the existence of God as a real thing, it certainly proves the existence of the collective consciousness of the idea of God. Whether there is a significant difference is not really a scientific question.
Whether the God meme can survive above the tribal social level is an open question that is evolving even as we speak, but that is a different topic entirely.