The fact that Halo 2 did more than 8 million on a 24 million install base has nothing to do with the 7th or 8th generation where Halo is no longer the top selling FPS, in fact, its not even half of what the top selling FPS sells.

It's true that smaller install base doesn't always mean a title will sell less than its previous counterpart but having a larger install base is one of the best ways of obtaining larger sales. There are other variables like marketing and metacritic/reviews but if you don't have a large enough install base then the games are not going to sell as well as previous generations especially considering how much more competitive this industry is compared to the 6th generation where all Xbox had for online was pretty much Halo.

The fact that some other FPS sold more then Halo dosn't mean it stole some of Halo gamer.

Halo 5 will probably come at holiday this year when it will released it should have at least 17 millions install base and since Halo is not a yearly IP it will have legs it should do 8 millions easily.

I'm gonna take a shot in the dark and say 9m. The lowest I see it doing LT is 8m.

halo actually is yearly

I didn't say it stole some of Halo's gamers, I said Halo is now in a very competitive space which is why Halo's attach rate has dipped so heavily compared to 6th gen. 8th gen Xbox owners have WAAAAY more to play than they did in the 6th gen, hence Halo 2's attach rate.

Halo reach came in 2010 and Halo 4 in 2012 it's not yearly

Your right if you pretend that the other Halo games don't exist.

combat evolved anniversary in 2011, spartan assault in 2013, master chief collection

You think that not mainline one will affect mainline one sale

OK you've put words in my mouth twice in a row now, I'm done.