Most of us know by now that Halo 5 sold considerably less than the previous installments. What do you think caused to impact sales so much?

Personally, I think its just the disappointment of Halo 4 tied with the MCC issues. I think Halo 5 could have sold quite a bit more just if MCC hadn't had the issues at launch.

There's only one answer and that's quality ... 

Halo 5 just isn't as good as the previous installments, plain and simple ...

Yeah I think that's exactly what's happened. Personaly though, I loved Halo 4 and yes MCC had issues but it's freaking awesome to replay all those Halo games in beautiful HD.  I encourage gamers to give Halo 5 a shot, it's worth it. I really like it anyways.

1. Halo MCC.
2. FPS doesn't need a savior in consoles. It's already established. No wow factor.
3. It's becoming more like COD.

1. Cod4 starting a revolution
2. Destiny

I've seen a ton of complaints all over the place online, complaining about the lack of local co-op.

Halo5: Halo is my main game series. 343 has driven the franchise in to the ground, they've tried to implement every single mechanic from every other FPS on the market, now they want to add Microtransactions. They cut out social playlists, some of the most popular gametypes like king of the hill and oddball. They took out staples of the Halo series like Forge and Firefight. The graphics are sht, the maps are sht. This company screwed everyone with Halo1Anniversary, Halo4, Halo:MCC, and no one was going in for another round in H5. Not to mention 343industries is simply a terrible studio, the aiming, hit boxes, bullet magnetism in this game are low quality. It's not a fun FPS. They need to find a better company and bring back classic Halo. Not to mention they basically tried to kill Master Chief, and he's only in 3 out of 15 missions in the game. Master Chief is the icon of the Xbox console, 343 is trying to kill him off makes no sense. 

I think its franchise fatigue combine with new developers.

Hmm
1.MCCand 343s reputation.
2. Halo is not as big as it was
3. Other big games coming out.

1. Halo MCC's debacle
2. The fact that the franchise should've ended in '07 when Bungie masterfully ended the original Halo trilogy.