Wouldn't Apple just have release it on Mac computers severely hurting its chances of being huge? 

Actually no. Steve Jobs was using Halo to prove Mac computers could handle high level graphics in games. Microsoft took it from under his nose and that threw him off. Halo was going to be the game that put the Mac on the map as an computer people could enjoy gaming on. Wherever Halo landed success would follow. Microsoft played it smart and bought bungie because Jobs didn't feel like buying them.

Jobs showing off Halo at CES on macs in circa 1999-2000 before Microsoft took it:

http://www.youtube.com/watch?v=Tzrme9yWens

P.S.

By taking Halo Microsoft essentially killed two birds with one stone. They held the credibility of Windows based gaming and also had the game that would give them their foot in the door in their war against Sony who threatened the multimedia and PC market with the first Playstation.

Wow, no wonder Jobs hated MS. 

But still, Windows was still much more popular than Mac even back then. Apple would need more than one game to convince gamers to buy a mac. Halo would have done well, but would never be as big as it is today. 

Yep. I edited my post and added more. Windows was far more popular than the Mac in those days but that was a smart yet dirty play. It worked though. Its not that Halo alone would sell the mac, its that it could prove that the Mac was a considerable non-console based platform akin to windows operating system PC's. Statistically speaking Halo was the prime reason people bought the Xbox. I would dare say a third of the people who bought Xboxes bought halo new and used. MS is one of the most hated companies, but makes the most because they will do whatever it takes to stay on top. Its not like they arent smart. 

That's true. Halo is much bigger than any of Xbox's other exclusives and is a big system seller. Wow, its very interesting how Halo started. Who would've known it would be so important for them.

Yep its the same reason why Activision (another American company with the same business sense as MS) bought bungie. If COD falls they need back up game to hold them for the the new gen. Also, if Microsoft ever dropped Halo they would be fucked (hence why three new chapters have been added to the story of Master Chief). Their first party is a testament to this truth. First party-wise MS is in the same position they were in with the original Xbox. They had Halo, a racer and Fable. Two gens later....essentially the same thing. Microsoft's massive success is attributed to third parties because they found the secret to Sony's success over Nintendo.

Halo became what it was because of the fact that it was a legitimate first person shooter on consoles. On the PC it would have just been another shooter. If even that. Also, Activision didn't buy Bungie. They are just in a publishing agreement. Kind of like what Sony used to have with thatgamecompany.

Goldeneye was the first legitimate shooter on consoles. Halo was a special game and Steve Jobs knew it. There was nothing as promising in 1999.

My post did not say "first legitimate". It said a legitimate.

And no, 007 was not as legitimate a FPS as Halo was.

Sony needs to steal the secret formula before its too late!