Great website for this is https://www.unseen64.net/beta-and-cancelled-videogames/
There was a build of Gears of War 3 practically finished for PlayStation 3. Similar to Gears E-day for PS5. Now if there is any surviving HDD out there with a build on there. We have no idea. It has yet to be found.
The other day I was reading old gaming magazines. One from 2006 had a 4 page spread on a *upcoming SEGA published game from Edge of Reality studios. A AAA M rated stealth action game called Cipher Complex. It never came out.
There are screenshots and a short video of Landstalker PSP. A remake of the Genesis game from Climax Studios. A build at some point existed.
Giest Force. SEGA Dreamcast. This one might be a grey area. The game was cancelled well into development. It was meant to be a US launch game. Supposedly Yuji Naka flexed his rank to be an asshole as usual. Had the game canned so he could steal the tech behind the games engine. Naka was a notorious asshole. I still hate him for this. Anyway, in 2011 or so fans found a DC dev kit with a build of the game. Fans did what they could to polish it up a little. Roughly 70% complete. However why I say grey area is a former dev later said what leaked is not the final build of the game before cancellation. So it's possible a near complete version of the game exists out there somewhere.
Bite my shiny metal cockpit!









