See, the thing about Halo is that despite being a huge fan, the story doesn't really do it for me anymore. I have played all of these games a billion times over, and will continue to play them a billion more times. I still appreciate some of the cool story moments and scenes, but whether or not the story is any good as a whole, is completely lost on me - with one exception. As a result, my enjoyment of the games mostly comes down to the weapon sandbox, the enemies, and the level design.
So yes, whilst Halo 3's story might not be as good as Halo 2's, I ultimately find the game infinitely more enjoyable.
1) Halo 3
2) Halo 3: ODST
Halo 3 and ODST are basically the same game. They share most of the same guns, and most of the same enemies. Halo 3 is just Halo perfection for me, because the enemies and the weapons are the most fun to use, and the game features the least amount of bullshit *shakes fist at Halo 2 jackal snipers*. Halo 3 edges out ODST though, solely because I slightly prefer its levels.
3) Halo Reach
Halo Reach is a cracking game, with a really gritty tone and environment. Sure, it can suffer from 2010's GREYBROWN, but it is still looks great, and the gameplay is fantastic too, with the most robust Covenant roster. The only real killer here, is the garbage vehicle health mechanic (which continues to plague the later games), and the weapon bloom, which is just frustrating.
4) Halo CE
Halo CE is basically a perfect example of design by subtraction, although this is more retroactive, than intentional. If you got a Halo game, and boiled down the whole experience to more or less its base mechanics, you would get Halo CE. Absolutely nothing is redundant or out of place. It is a solid game, and the gameplay more than holds up almost 20 years later (except the Scorpion tank). The only real downside is that I just don't really enjoy the levels too much. The first half of the game is fine, but the second is basically just the first half, but in reverse, and with the Flood. *shakes fist at rocket flood*
5) Halo 2
I just don't like Halo 2's campaign levels. I don't mind most of the Master Chief's levels, but the Arbiter's levels are just a drag, because you spend half of the game is just fighting flood, sentinels, or brutes - and just... eh. Out of Bungie's games, this is definitely the one I want to replay, the least.
6) Halo 5
Whilst the other games are protected by precious nostalgia, this one definitely isnt. Whilst the weapons are probably some of the best in the series, the levels are completely forgettable, and the prometheans continue to bog down the experience. This is the only game where the story actively annoys me, too. Also, *shakes fist at the Warden Eternal*.
7) Halo 4
Halo 4 is basically the perfect storm of bad weapons, bad enemies, and bad level design. The prometheans are frustrating to fight, the new weapons are either boring or useless, and the levels somehow just make everything worse. Im currently also slogging my way through Halo 4's Spartan Ops mode, solo/legendary, so that might also be tainting my perception of this game. Whilst I am usually a bit wishy washy with Halo 4, at the moment I just can't stand it.