After the recent SD post, I went and read the entirety of Black Summer. That it's not really very original doesn't detract from its interest, although it was so Bush-specific (without ever naming him) that I suspect it won't age very well. In that sense, it's a lighter version of Kingdom Come, without the biblical approach and gravitas of the narrative, not to mention the art. The carnage is more graphic (although I think the Kansas Incident was worse in any objective sense), but, well, these are clearly just people with powers. They have no other narrative or social standing, which I think is closer to how our world works than DC.
In some aspects, the Kingdom Come disaster comes because Superman couldn't be anything else than Superman, and the Black Summer disaster comes because John Horus tried to do what he thinks Superman should do, but because he isn't Superman, it doesn't work.
The question remains: would it work if Superman did it? A Better World *dared* to suggest that yes, up to a point, it would. That's one of the moments in which comics mythology came the closest to implode and break under the weight of its own contradictions without approaching it from the satirical or the grotesque, and it's still pivotal, I think, to understanding the DC multiverse.
You can't quite do the Superman thing with other characters (e.g., Apollo or Majestic), because, fantastic and interesting as they are, they just don't have the same narrative and cultural specific weight, both intra- and inter-textually. I mean, even leaving aside the latest, not lamented at all Superman movie, the Christological element has always been clear in all sorts of ways (although some writers have tried to go for a more Greek-like approach, e.g. Morrison's JLA).
Perhaps it'd be interesting to compare the Lords' Earth of A Better World with descriptions of how some Christians expect a post-Second Coming kingdom of Jesus on Earth to look like. In a way, Superman *is* the all-powerful man-and-God who never sought secular power (in his case, defending individual lives, etc). And DC 1,000,000 was practically explicit in their apotheosis of late-future!Superman. So you might very well look at A Better World as what'd happened if at some point during the Calvary Jesus would have dropped the cross and said "You know what, fuck this, let's do it the direct way. I'm going to fix _this_ world, and I'm going to do it _now_."
While standing over the burnt ashes of the Roman Emperor.