How I read the OP (at least for this bullet) is in line with what I remember at the time: Halo was originally a Mac exclusive, and us Mac gamers (there were dozens of us, dozens!) generally perceived it as being the beginning of a golden era, where Mac would be taken as seriously as PC for games. I was absolutely heartbroken when it moved to XBox exclusive. I still ended up buying one for Halo anyway, just like everyone else.
EDIT: that being said, I was a kid at the time, and reading up on things, it was announced by Jobs during MacWorld that it was going to be Mac + Windows, so I don't know if my memory of the situation is about rumors before launch, if I misunderstood things because I was 13 at the time, or if I simply have mis-remembered because that was over 20 years ago, hah.