It was originally suppose to be an Apple game right? Microsoft would have had to figure something else out to be relevant. I wonder if it would have changed anything with Apple's gaming vs pc.

Og Xbox without Halo is just a bigger failure.

Xbox (the brand) would be long gone, X360 would never be a rival to PS3 without Halo 3 gargantuan success.

So the consensus thus far is they would have done disastrously, but to what extent do you think, like would they still have outsold the Dreamcast (I know Wman thinks yes) would the 360 even have been a thing?

My first thought when reading the thread title was "dead on arrival". I'm not sure how close that is, but I'm pretty sure it's close enough to not give it much more thought. I guess there's the chance they could've snatched something else instead, but I certainly wouldn't bet on it.

It is hard to imagine it doing well without Halo, Dreamcast numbers is maybe possible.
5-10 million perhaps, it was strong hardware, could get solid third party support and Microsoft had a fairly strong brand back then.
If they had an alternative launch IP/game they could put their weight and marketing behind the way they did for Halo, they could have had another killer app instead, but I don’t know what it would be. Securing exclusive GTA III perhaps? Get ID to make a DOOM game?