Demigods is a modern-day, magical-realism role-playing game in which all of the gods are real and every belief system is correct, at the same time. In this world, all of the gods exist because humans imagined them into existence. So there are at least a dozen different sun gods, for example, pushing, pulling, or being the sun, while at the same time the Earth is ninety-three million miles away from the giant fusion engine it revolves around. Multiple truths! All at once! Have fun with it.
So while the big main religions are still the big ones in the world of Demigods, driving down the street you might also see a temple to Odin, or a shrine to Aphrodite, etc. Mortals don’t know the gods are real, but there are greater numbers of people still following smaller religions. Additionally, their incredible power of imagination helps mortals edit things they definitely don’t want to see. So when a seven-foot-tall demon walks into the coffee shop they just see a very tall lady and ignore the bright red skin, horns, and spiky tail.