That doesn't confirm anything and is based off a series sell in number, not a specific title sell in number. 

We have no lifetime numbers, but it is pretty much accepted it is above 5 million by now by many media outlets same with titan fall.

The thing is other mega series like cod,  minecraft,  gta etc are on multiple platforms.  Now gta doesn't get milked and it's top top quality so it's still growing,  but cod is seeing a similar decline as halo although lesser.  

The thing with cod is,  it's not confined to just xbox.  So it remains bigger for longer and if one console fails it doesn't.  

Microsoft are making a lot of money by keeping minecraft on Playstation and PC. And soon Nintendo.  

Maybe they'll consider making halo multiplatform in future. Maybe not Playstation and Nintendo but at least pc where pc fans and many Playstation and Nintendo fans could play.  

Halo 6 will probably see another decline if they say xbox one only.  such a waste of revenue in a sector of their business they need to stop bleeding money. 

Ahhh you're confusing what I'm saying.

The series is declining from the game I've aleady played. GT5 and GT6 just seem dated, jumbled mess of a single player mode, not enough strucutre, dated UI and a lackluster online. Can I play them and still have fun, sure, but it's no longer on top of the racing genre, it's losing its appeal.

Can GT Sport be a return to form, of course it can. From what I've seen no. If Polyphony Digital do not make me feel like it's going to be a return to form, why should I expect it. It's their job to convince me, not me to convince myself and certainly not some random forum guy with to much emotional attachment to GT who can't take other peoples critical opinions on.

Halo 5 will not lose them millions but MS will expect a certain amount of profit. The more they spend, the more profit they will want it return. Halo 5's budget for developing and marketing will be the biggest of all their games and MS will want a decent return.

The losing millions part is referring to their next Halo. For arguments sake let's say Halo 5 sells 5M ltd. Do they reduce the resources and development budget execting Halo 6 to sell around 5M and risk further decline for the series or allow a development and marketing budget to try and boost the series back up to 10M + ltd (bare in mind trying to increase sales to a 10M will cost a lot more than trying to maintain a seris at 10M). Of course they could spend all that money and it only sells 5M again so risking losing money or making very little and the return not representing the investment.

"Decline" means "gradual or continuous loss of strength, quality, numbers, etc". Compared to prior releases, Halo 5 fell off a cliff. This whole gen, MS has been bragging that the XBOne has "sold more than the 360 in the same time period", so install base isn't the excuse here, because Halo 3 was massive. 

And I don't know how to maintain popularity, I'm not a developer =/. But it's not like it's impossible. MGS hasn't declined. GTA has increased in popularity (I always made the argument, last gen, that multiplatform doesn't increase the fan base; it splits it. All the game franchises that lost PS3 exclusivity and came out on 360: their total sales were about equal to their PS2 counterpart. Even GTA4. Yet, games that stayed PS3 exclusive also sold in line with their PS2 counterpart. Main example being MGS4. GTA5 came in and bucked that trend, though, and sold way more). Fallout hasn't declined. 

Is it so hard to believe that the switching of developers eventually raised some issues? Once West and Zampella left IW, nobody questioned that the CoD decline was due to lower quality development, after MW3 released (much like how Halo 4 released from 343i, but people complained about the game after the fact), and not due to the age of the franchise. But when the same switch in devs happens with Halo, the series declines because it's "old"? And has nothing to do with the sour taste left in people's mouth from 343i's Halo 4 multiplayer, that never occured with the original developer, and the botched launch of the MCC? 

PS2 had a userbase almost as big as PS360 have together.

About Halo sales:
Halo 3 was the (retail) peak. Roughly doubled Halo 2 sales. But at that time there weren't that much other FPS with a really great MP. And it had the effect that many early games on a platform share.
Look at GT, MGS or FF. FF VII sold way more than VIII and IX. And FF X again sold better tha the late FF XII.

So with some usual effects for later sequels on a specific platform you can't really say that Halo declined after 3. If there's a decline it happened on Xbox One.

The numbers were low because all of multiplat fans jumped ship back to Sony. Exclusives get an extra boost from the crowd who is going to buy consoles and the crowd thats already there. Guaranteed, Sony would never have sold a million copies of some of their exclusives if that hardcore multiplat audience hadnt been gobbling up the few big exclusives Sony could offer. Next year is different. Sony has some legitimate games and because those core gamers they will sell very well. Microsoft is going to have to rely on the legs of the holiday season.

This topic is derailing the OT. But again please tell me what you saw?

GT sport return to form! return from where? THIS IS NOT A GT7, its a different series. And the way you form an opinion, it doesnt matter what they show, you wont be impressed any how. Speaking about mainline series, that is one game GT6 that dropped in terms of sales and everyone will agree that the drop was due to poor release window and GT wasnt the only game that suffered because of New Consoles. And to say something is declining it should have a downward trajectory over few entries Like Halo, only if one game fails to sell thats called a dip. No body said after forza 5's dissappointment that Forza Horizon will suck, and that the series is on decline. I enjoyed GT6 more than Forza 5, GT6 scored better than forza 5, but "FUN" is subjective. As for sales everyone knows why it didnt do well.

I m not emotionally attached to the series I am a racing fan, the only thing bugged me about your post is that you came up with your own version of why GTsport will suck, based on the last game didnt sell well, didnt score well, and you didnt enjoy it, even though its not a GT7 and you call that a "critical opinion".

Completely agree. The sales of all the Halo games must be seen in the context of the platform they were on. With the original Xbox, these games were the only selling point. With 360, MS achieved the"shooter box" status early on. A lot of these shooter fans now are on PlayStation and we will see a decline. I'm guessing Halo 5 will have strong legs because of its strong MP, but will maybe reach 75% at most of Halo 4.