75% of Halo 4 wouldn't be far from 7.5m and that would be pretty good actually.

MGS4: sold in line with prior MGSs. Didn't need to be multiplatform 

GT5: sold in line with prior GTs. Didn't need to be multiplatform (albeit, that would never happen anyway). In fact, PS franchises in general sold in line with their PS2 counterparts, and PS3 had half the userbase of PS2. And if not the same franchise, then the same developer (Uncharted vs Jak, Infamous vs Sly, etc) sold in line or better than their prior work, despite being handicapped by half the prior userbase.

Point being, userbase doesn't have everthing to do with it (whether comparing Halo to prior Halos or multiplatform games to prior exclusive games). XBOne "has more consoles sold than XB360 in the same time period", Halo 5 came out in the same time window Halo 3 came out (almost 2 years after the console released), it's the "first Halo (proper) on the console" (that "effect that many early games" you referred to) which apparently means people were just salivating to get it, and whatever factors MS likes to point out. Yet, it sold less than 1M in the US, which isn't bad, in a vacuum, but bad for the bread and butter flagship MS title when you know what the series is truly capable of. 

I think it's better to accept that 343i just isn't as capable of making compelling Halo games, instead of just blaming it on "well, the franchise is old anyway". 

All these years on this site, and people always talked about "you can't play sales" (pretty much the PS3 fan motto from 2006 until like 2012) and that it's all about quality, but now there's a dip in quality to a franchise and for obvious reasons (developer change) and nobody wants to acknowledge it, and instead say that it's because the franchise is old. It's perplexing. Especially because there's old franchises to this day selling well. Street Fighter, Gran Turismo, GTA, Metal Gear Solid, Tomb Raider, Resident Evil, Forza, etc. 

I bet when Gears releases and doesn't do as well as prior Gears, nobody will flinch to say Black Tusk (or The Coalition. Whatever they're going by) < Epic Games. 

Halo 5 is compelling actually. Except for sales. It scored lower on metacritic but most sequels do at the moment.

I wouldn't say that it has anything to do with the age. Right now I miss reliable digital sales data. Not expecting that much but it seems digital sales weren't that small.

Like I said, too emotionally attached. Let's leave it at that because clearly you won't allow anybody to have their opinion. You ignore 50% of what I say or you just don't connect the dots. Not going to keep going around in circles. Stay in your "gt is amazballz" bubble. Over and out!

Dat Destiny effect

I don't think anyone here said Halo declines because it's old. I said the decline is easy to understand, many factors change during that timeframe and different devs, bad launch of the MCC, strong competition on FPS market, multiplat gamers moving to PS4 for example all have an effect. I've also not used install base as an excuse, because I'm happy to see millions of people bought X1 for other good reasons than Halo :)

But I can't agree with you that it's Halos quality that has declined. I think the opposite as I never liked Bungies Halo much, but I find 343is take on Halo very refresing and high quality, from gameplay perspective. Online experience is superb. And it's also getting good reviews. That said, they probably failed to keep original fans satisfied enough and failed to bring in enough new fans to maintain sales. Then again like a said, it's just a first-person shooter among others so I'm not sure if it was even possible to make enough new fans along the way to maintain its insane popularity.  But who knows, maybe you're right, 343i made a good fps-shooter but not good Halo and all the blame goes to them.

Hey it's nice to see you brought up Gears of War, my favourite franchise :P To quote you "I bet when Gears releases and doesn't do as well as prior Gears, nobody will flinch to say Black Tusk (or The Coalition. Whatever they're going by) < Epic Games."

Sure some would say that but they wouldn't know what they're talking about. Epic Games tanked GoW with Judgment themselves. Since GoW2 there's been constant complaining about Epic and the direction where they took the franchise. Fanbase is divided between original fans and fans of GoW3 and instead making Judgment compelling to both sides or one of them, they made a game that wasn't compelling to either :) 

That puts The Coalition in a sweet but challenging position I think, but that's a whole other topic.

They sacrificred Split-screen so the game could be 60 FPS.  I dunno about you, but Halo feels like a broader and more expansive story under 343.

There's two sides about story and storytelling.
343i's storytelling is just lightyears ahead of what Bungie did.
Then there's the basic storyline, where 343i to often falls flat, at least until now.
Characterization is way better now. Except Locke. I neither like him nor do i think he's interesting.

But Halo 5 really felt like they could have done more. I really hope that 6 will improve. And i actually hope we see the rest of team osiris again.

Yep, when the multiplat fans jumped ship to the 360 from the PS2 that instantly increased the sales potential of any Halo on the 360 platform. Halo 5 definitely has strong multiplayer, so yes, I agree that it will go have legs throughout the holiday season selling 3.5 to 4 million by years end. Remember that Black Friday and Cyber monday are coming as well and Microsoft is known for beating Sony on Black Fridays.