I hear Uncharted this and Uncharted that, but the simple fact is that Halo is simply in a different league when we're discussing sales in the US market. It's not even close... Really, it's just not. In addition you have Call of Duty, which is also bigger in the US on Xbox than it is on PS4. Those 2 games alone will keep Xbox competitive short term in the US.
In the short term, Xbox One will keep the gap small and possibly even take a lead. Long term? Who knows. The generation is too young.
Halo isn't what it once was, both brands(halo and xbox) have been damaged.
Can you elaborate on that?
Other than having MMC being bugged (but selling very well for an HD remake), I do not see what can make you affirm that?
If you look at the last full game, Halo 4, and same timeframe sales, maybe Halo 4 is not the beast that Halo 3 was but it is certainly NOT a decline compared to other versions, so other than you personnal fillings, I'm curious to see how you came to this conclusion...
Same goes for the Xbox brand by the way, as the Xbox One is doing very well compared to then Xbox 360 for instance.
Edit: Oh you are another of this alts, so I guess this post was not serious. My bad.