While the world is Batman: Arkham Asylum.
Earlier this month developer 'Salvatrix' – who also worked on Rift and Rogue Squadron III: Rebel Strike – posted a thread on Twitter and spoke on Reddit giving many previously unrevealed facts, images, and even videos from the cancelled Superman game, codenamed 'Blue Steel'. The project was known about before, but not in this much detail.
According to Salvatrix, the project would not have been an open-world game, with largish open maps at around 20-25 blocks across Metropolis, Smallville, the Fortress of Solitude, and even the hellish planet Apokolips. Superman would've been able to fly around and fight "with foes more in his power range" rather than the usual "kryptonite and fighting robots."
Superman would be able to pick up and use objects from around the world to fight enemies, and even punch them through buildings. Villains would include Darkseid, Livewire, and Doomsday, as revealed in some excellent concept art.
Just for fun, here is some of the art explorations that were done as well…#gamedevelopment #gamedesign pic.twitter.com/NvvBapJSR7
— Salvatrix (@DevSalvatrix) July 14, 2021
While most of the screenshots are blocky, Salvatrix also posted a gameplay prototype with updated assets, which you can see below. It shows off the interesting combat system, including the spectacular building rushes – and perhaps most interestingly of all, Kryptonian villain General Zod would've been playable during the story and not just during the game's versus mode.

While the project was cancelled in 2008 because the financial crisis at the time that killed both Factor 5 and publisher Brash Entertainment, it was meant to come out around 2009 alongside Batman: Arkham Asylum and the also-cancelled sequel to Superman Returns. Still, it's a fascinating glimpse into a promising game.
Hopefully Gotham Knights developer WB Montreal is a Rogue Squadron movie coming from the director of Superman's fellow Justice Leaguer Wonder Woman.