All I'm seeing here is "this game's X with that game's Y" (and The Game which I subsequently lost). When the OP said Perfect Game, I thought back to the impossible beast I've been thinking of for years.
This Game is nearly impossible for me to explain politely, so I'll be blunt. The Player is God. Not a Christian god, not a Judaic god, not an Islamic god, just simply an all powerful being with complete control and power. That alone sounds like fun, but I also enjoyed the Sims and RTK8 when I was younger and they left an impression on me. I'd like to have a living, functioning world, where the Player could inhabit one Character at a time and experience the world around them at that time. Have a character grow and age with society around them. Become a driving force in history or merely a pawn to an ambitious NPC.
It would include an effective timeline, where a Deity could go ahead fifty or a hundred years and see the consequences of past actions. Each time the Player wanted to start a new world there would be settings from the type of inhabitants to the magic available, to the landmass and basic geological functions. Or you could just hit random a few times, too. There could be a large Pantheon of Gods and Demigods and such, or a monotheistic reality. Artifacts like flaming swords and such could appear and create legends and history that one could play through.
To make things more difficult, however, are a few nuances. Player can only travel forward in time, not back. Must earn God Mode, by destroying the current deity, or something else similar. Possible side rule of Character Inhabitation, once you "leave" a character, you cannot return.
There are many, many possibilities here. Like cultivating germs in a lab, one could seclude a village with some mutation and have fun with the results. One could have "Bloodline Artifacts", a Sword that will only ignite if held by a descendant of "Bob". May even be reason enough for hereditary rule.
This is the Perfect Game in my head. This is what I think about when I have nothing to think about. I'll never play this game, I doubt it will ever be made. But damn, it looks fun!