Gorelab- That's an excellent observation. The Devil Summoner subseries in the Megami Tensei umbrella loves alternate realities. Heck, the previous Devil Summoner games (Devil Summoner and Devil Summoner 2: Soul Hackers) were themselves an alternate reality on the SMT realm.
See, partway through SMT 1
US President Thorman sets off a bunch of ICB missiles that decimate Tokyo and plunge the world into an apocalypse. Hence, SMT 2 is set in the post apocalyptic future.
But Devil Summoner takes a whole "what if?" regarding that whole scenario. In those games,
US President Thorman is killed and the missiles don't go off.
So everything turns out differently.
With SMT, your main enemy is "God" but in Devil Summoner, your main enemy is more tangible; Sid Davis in Devil Summoner and his Phantom Society in Soul Hackers.
One thing the Devil Summoner games added to the SMT formula was the idea of "demon loyalty" where you had to give your minions tokens and such to keep them loyal to you, or they wouldn't do your bidding in battle. From what I understand, it got ridiculous in the first game and horribly skewed the difficulty balance. I liked the GUMP (GUn type coMPuter) that the Devil Summoner protagonists got to equip. More cumbersome than the arm-type computers from SMT, but certainly more badassed.
I remember in the interview in the Eternal Punishment fandisk that Kaneko and Okada wanted to have a MegaTen game set in an earlier era, because though the games were usually set in modern or post-modern times, the whole idea of persona, demonology/ demon summoning, and all the dark spirituality are concepts that are universal throughout time and were oftentimes a greater part of more ancient cultures when people believed more in magic than in science.