Halo reach by a LANDSLIDE. The campaign was shockingly good, and the tagline "from The beginning, you know the end" just tells ya everything. It makes ya dread the ending, as the terror of the covenant army and their seemlingly limitless troops overwhelm you,
and the people around you die like flies. And then the multiplayer for some reason really convinced me it was great. I will say that that armor shield thing was a huge piece of crap that just completely put a stop to the smooth flow of messy, plasma filled warfare.

I suppose halo 3 would be a close second. And then halo odst after that.

 

2 is the best, no question. It improved on Halo 1 in almost every way. It changed the landscape of online gaming. Halo 2 had the best online in the series. Simple arena pvp gameplay. Halo 2 does have issues specifically its legendary difficulty.

Halo 3 would be 2nd but I found it to be to similar to 2 just in HD which isn’t bad. It gave the series a satisfying ending.

I don’t understand people’s love for Reach. I just played it recently on the MCC. The story to me is not engaging. The Fall of Reach book was better. I didn’t care for any of the Spartans. Noble 6 was a Master Chief knock off with less personality. The rest of Noble team was a bunch of generic throw away dudes that only characteristic was I’m a spartan and I’m a badass. Campaign just took the best parts of 1 & 2 and re structured them. Online was okay. I hated the armor abilities. Fire fight was a nice addition.

 

Alright.
Halo 1 is where everything started. It's the most fair gameplay wise. Whenever you die, it's most likely your fault. Yeah, somethings didn't age well, like the graphics, but it definitely evolved shooters for home consoles, and is being copied to this day.
Out of all of them Halo 2 had my favorite campaign. With a good plot, introducing the Arbiter, and solid gameplay. This was also the first game that made people give a shit about Xbox Live. Even if Legendary was bullshit, and the Multiplayer had too many exploits like button combos.
Halo 3 is probably the best in the series. As it was more polished than 2, and got the best parts of 1. It also had the best multiplayer, and is still a fun time 13 years later, the hype was real.
Reach is the last Bungie game. And returns to Halo 1 style of gameplay. It's good, but I prefer the others. And the story is dark.
4, is the weakest. As it felt like it was trying to be COD, while at the same time trying to be Halo. The campaign does have alot of nice set pieces, and characterizes Chief and Cortana more, but this game has a polarized fanbase.
5, has the second best multiplayer. The campaign is whack though, but it multiplayer is probably the best in the series.

Halo 3, is the best for improving on everything and it's fantastic gameplay. It definitely finishes the fight.
Halo 4 is the weakest, but it's far from bad.
If you wanna talk bad, look at MCC before Microsoft got their shit together.

 

H1 just bc that game alone bring back so much memories of playing with my friends all night long multiplayer. We had so many epic and funny ass moments during CTF on Blood Gulch.