I enjoyed Infinite Crisis at the time if only because I was thrilled to see the Multiverse reintroduced along with Kal-L and Superboy Prime. I was disgusted to see how both were treated but was happy overall with the changes IC made to DC continuity, especially restoring Silver/Bronze Age elements to Superman's mythology.
In hindsight, I think it's needlessly dark and depressing (thanks to Dan DiDio and not Geoff Johns) and I would have preferred a sequel that reintroduced the Multiverse while also adjusting DC's continuity of the time without wholesale deconstruction and murder.
If I were writing a sequel to COIE set twenty years later, I would have done much of what Johns did but would have gone for a very different tone and outcome overall.
Some bullet points:
- Alexander Luthor, Kal-L, Lois, and Superboy Prime return. Luthor is the main villain, though we learn that a remnant of the Anti-Monitor's consciousness entered Luthor just before he and the other survivors left for "paradise." He's been slowly consumed by the Anti-Monitor's presence.
- Luthor convinces Kal-L and Superboy Prime that "New Earth" needs to be replaced but his true goal is to restore the infinite Multiverse so that he can destroy it again.
- The "paradise" dimension was what we saw in Kingdom Come: The Kingdom, a copy of Earth-Two but with only two superheroes: Kal-L and Superboy.
- Kal-L and Lois have served as surrogate parents to Superboy. Though time had no meaning, he's developed into a heroic young man as a result.
- The first goal of Luthor's plan is to separate New Earth into its constituent parts: Earth-One, Earth-Two, Earth-Four, Earth-S, and Earth-X. This happens by the end of the second issue and leads to respective characters returning to their original Earths and universes.
- The Anti-Monitor fully consumes Luthor and accesses Qward. He then creates and destroys new universes, quickly growing in power.
- Alexander Luthor leads Kal-L, Superboy, and the heroes and villains of five Earths in battle with the Anti-Monitor. Barry Allen returns from the Speed Force and aids the heroes in weakening the Anti-Monitor before imprisoning him in the Source Wall.
- In the aftermath, a new Multiverse has been created, consisting of Earth- One, Earth-Two, a new Earth-Three, Earth-Four, Earth-5 (former Earth-S), Earth-10 (former Earth-X), and unknown universes that together number eighty-six.
- Kal-L and Lois return to Earth-Two and retired to a farm in Smallville.
- After reconnecting with Iris, Wally, and Bart, Barry sets off to help Superboy Prime find Earth-Prime and explore the new Multiverse in the process.
- Though New Earth has been separated, continuity from 1985-2011 is largely intact. JSA/JLA and other character team-ups happened through dimensional travel as was the case pre-COIE. Team-ups and Multiversal travel is again possible and happens frequently.
- One of the new eighty-five universes is Universe-Zero, with a continuity completely rolled back: no JLA, no Robin, no Titans. This universe would be home to an "Ultimate DC" in the vein of the New 52 and the Earth-One OGNs.