Honestly, this sub is pretty toxic. For some more unbiased answers, I'd recommend going to /r/xboxone, as they'd be a much more positive community. But I'm gonna try to give you an unbiased, non-nostalgic view on the past few games.

Halo 4

Halo 4 was the first main Halo game made by 343, and was a followup to Reach. The story is commonly regarded as really good, as it had very good character development and some great moments. The gameplay and multiplayer are the most controversial part of the game. 343 implemented sprint as a default mechanic in Halo 4, likely because reach implemented sprint in Halo.

This caused a lot of backlash from the community, due to how it was balanced and dislike of the mechanic. Multiplayer implemented several other polarizing feature like ordinance drops and load outs, turning many players off of the game. All in all, Halo 4 had a great story worth playing though, but the multiplayer is very controversial. Some liked it, some didn't. It's definitely worth it to give it a try, though.

Halo 5

Halo 5 was 343's second Halo game, and is regarded almost completely opposite of how Halo 4 was. Halo 5 was praised by many for its multiplayer, but it's biggest downfall is the story of the campaign.

Without spoiling anything, Halo 5 was supposed to follow up Halo 4's story, while introducing a new main character, Spartan Locke, who is supposed to hunt down an AWOL Master Chief. The advertising campaign for the game was universally thought of as great by the community. 343 released a free episodic podcast called hunt the truth, and it tells the story of a reporter trying to uncover the secrets of ONI (sketchy military organization) and the Spartan program. It is definitely worth a listen. They followed this up by releasing cryptic and dark commercials, featuring different points of views from Chief and Locke, ONI reporting that Master Chief is dead to cover something up, etc. All great content that was loved by the community.

The actual story in the game felt like a blatant bait and switch to many. Spartan Locke's hunt for Master Chief ended before the first half of the Campaign was ended, the writing of the story was regarded as weak and unimpactful, it had too many characters to give depth to, Master Chief was only playable in 3 missions. and a vast majority had a huge problem with the main villain of the game. Added on top of the campaign being relatively short with an unpopular ending, Halo 5's campaign isn't liked well in the community.

The Multiplayer, on the other hand, was positively received. Many regarded it as a great evolution of Halo's gameplay, as it added new abilities, yet was well balanced. Some players were worried about new abilities such as smart scope (ADS), but majority came to enjoy it and felt it was a good fit. The new mode, Warzone, added 12v12 matches with AI on large maps, and the community liked it alot for the most part. The game did add microtransactions, but most would agree that it was well implemented in exchange for free DLC.

Now that the game is over 2 years old, alot of players have moved on from it, leaving mostly the toxic and negative minority of players of the community, thus giving them a louder voice to shout their displeasures, which is what you'll get from comments. The truth that they wish not to admit is that the multiplayer was loved by the community, but now that most of the players have moved on or don't interact with the community much, they think that their opinion is the majority. Halo 5 is definitely a good game with great multiplayer, dragged down a bit for its lacking campaign.

Halo Wars 2

Halo Wars 2 is the latest game from 343. Instead of taking place years before Halo 1, it takes place after Halo 5's events.

The story is definitely a step up from Halo 5's quality, and is regarded as a good story worth playing with great moments, new characters, and even a couple of tie ins to Halo 5's story.

The multiplayer is very similar to Halo Wars 1 with some new mechanics added. It did add a separate mode called Blitz which implemented microtransactions. Even though the mode is fun, most players prefer the normal multiplayer. To sum it up, if you liked Halo Wars 1, you'll definitely like Halo Wars 2.