Halo is a great game, but it seems it was 'rushed' to be done in time for the launch. The game has both it's high and it's low points. Originally in the Mac version, you were supposed to be able to go 'everywhere' in Halo and find your own way. In the XBox version, you are limited to where you can go and your path is really set for you. (Basically kill the aliens until you reach the end of the level).
The graphics of the game are great, I like the weapons, and driving around in the vehicles is really cool.
If you can get two XBoxes in one place, you an have a really fun team deathmatch where your opponents can't see your part of the screen.
If the game had been Mac only, more iMacs would have been sold. People have been buying the XBox to play this game.
But apparently, Microsoft is only making this a Mac game because of the 5 year agreement with Apple. I read that in their contract, if Microsoft announces a product for the Mac OS and it is ever released for any platform, it had to be released for the Mac OS (they couldn't discontinue development). When Microsoft bought Bungie, they decided to make Halo an 'XBox exclusive', but since they had their agreement with Apple and it had already been announced for the Mac, they had to continue development and release it.
When they realized that they were going to have to release the game on the Mac any way, they just decided to release the PC version as well because it would look bad for them if they said that the game could only run on the 'Powerful XBox' and not the Windows PC, and then they released it on the Mac.
It's a pretty interesting story, don't you think?