The Halo series is so intrinsically connected to the Xbox that it's hard to believe that Master Chief could have possibly shown up on any other console. It was a very shrewd move by Bill Gates and company to purchase the rights to the Flood-blasting franchise. Without Halo, there's a strong chance that Microsoft would have been knocked out of the console war entirely.
But while these games are forever linked to the Xbox now they were originally intended to be a cross-platform release. As crazy as it sounds Halo was close to appearing on the Playstation 2, which would have been yet another feather in the cap of Sony, but could have been disastrous for Microsoft.
Sony Says Goodbye And Microsoft Says Halo
When the original Xbox launched - not the Xbox One as that was the third console...yes that's still dumb - it was joined by Halo on its release day. Up until this point, first-person shooters hadn't been done well on consoles as developers hadn't quite figured out how to adapt the controls of a genre meant for mouse and keyboard to a controller. Halo was one of the earliest examples of a high-quality console shooter which led to it becoming a massive success. It would go on to sell millions of copies along with millions of Xbox systems allowing Microsoft to remain a vital part of the video game industry for the past two decades.
But this was never the intended plan for Bungie. Back in the halcyon decade of the 1990s, they were a small company working on a real-time strategy game that would eventually morph into Halo. They never had any intention of making the game exclusive to any one console. It was originally slated to release on whatever systems it could including Apple computers. Steve Jobs even introduced it during the 1999 Macworld Conference & Expo, although that announcement ultimately didn't amount to much due to Apple's lackadaisical approach to gaming.
Since Sony was one of the biggest players in the console race at the time Bungie planned for Halo to be ported to the Playstation 2. The port got incredibly close to completion, to the point that footage of it running on the hardware is available for all to see.
As far as we know this is all the evidence that exists of a PS2 Halo release. Obviously, it looks a little rough now, but all the pieces are there. Master Chief shows up with a rocket launcher, Covenant Elites are flying around in Phantoms and Ghosts, etc. It's a Halo game meant to be played with a Dualshock controller, which just sounds insane.
What's even more bizarre about this is who was originally going to publish the title: Rockstar. The Grand Theft Auto maker was in charge of organizing Halo's console release. That means there's an alternate future where Rockstar not only makes billions off of GTA and Red Dead Redemption but also holds the rights to Halo. At that point, they'd have so much money that they could buy Los Angeles and turn it into a real-life version of GTA Online.
But as we all know, before Master Chief could share the spotlight with Jak & Daxter and Kratos, Microsoft swooped in and bought Bungie along with the rights to Halo. Bungie had been having financial troubles, so when the purveyors of the Xbox offered to acquire them they took the deal. Soon after, Halo was adapted for the newest addition to the console race and history was made.
Oh What Could Have Been
Since then, Bungie has moved away from developing Halo games. After a brief yet tumultuous period working for Activision, they're still out there making new content for their current IP, Destiny 2. Meanwhile, Halo continues to be Microsoft's number one franchise with Halo: Infinite expected to release alongside the Xbox Series X this holiday season.
As for Sony, considering that they're about to drop the Playstation 5 to compete with Microsoft's little black gaming box, it's safe to say that they survived not having a Halo game to call their own.
Source: Lost Media Wiki