Halo 2's single player campaign is criticized for being short, and ending on a cliffhanger. I agree, because I was able to finish it in 3 days. Compare it to the original Portal: it says what it needs to (and more if you're observant), and doesn't overstay its welcome. Before I shot a gun, I practically had an encyclopedic knowledge about the Covenant compared to the first game.
The last game only poked at what the Covenant was. The opening cinematic shows the Covenant general that was in charge of capturing the Halo (that blew up) testifying before his bosses. Between shots of Master Chief and friends receiving metals and ribbons, the alien general gets branded a heretic for his failure, complete with a hot metal poker! After saving Earth as Chief (all in a day's work), the hot poker guy gets dragged past space jail, and is sentenced to death by suicide mission. In so doing, he's promoted to Arbiter and gets some fancy armor. Then, I'm the one wearing his alien boots and wondering what happened. Can't I take my chances in space jail?
The entire campaign tosses you back and forth between Chief and Arbiter every mission or two. If in doubt over who you're playing, this game renders your feet, so just look down. I think this might be Bungie's RTS roots shining through. What would become Halo started off as an RTS game, and those games almost always have you play as the other faction. I can't tell if that's always been an RTS thing, or if Blizzard started it. Either way, the other guy's shoes are a brilliant way of showing story instead of telling story. I wondered when Chief and Arbiter would fight each other, but they don't. By the end of the game, I liked the Arbiter more, because he had a perspective transformation, and even some redemption.
Level design is greatly improved, to the point where I wasn't outright annoyed by any of them. There are a few palindromic levels that you have to fight your way in, then out of. I can dig this, because you often go in and out of places the same way in real life, and don't teleport around. Yes, teleportation is a thing in the Halo universe, and even Bungie have joked that if you want to get around fast, you teleport!
Weapon variety has expanded. There's "battle rifles" and SMGs instead of the default "assault rifle" of the original. You can now use Covenant energy swords, which are insanely powerful as they usually one hit kill. Besides the plasma rifle, there's the brute plasma rifle, but I haven't noticed any difference between them.
Due to bugs, I'm not sure if the original had dual wielding weapons, but I made extensive use of it here. If you have identical weapons that are dual wieldable, do it. Plasma weapons are both effective and ubiquitous, so dual wielding them gives you god-like destructive powers. Since damage output is spread over 2 weapons, they overheat less if you stop firing them after each kill. If you throw a grenade or switch weapons while dual wielding, you drop a gun (but don't switch weapons).
Each character has regenerating shields (like a lot of games since this one was released, ~2004), but you have a health pool that also regenerates. It effectively works as more shields, but there's no health bar displayed, so you have to guess how much you have. This has side effects of eliminating health packs from around levels, and forcing frantic decisions of whether to take cover or to try taking the guy out. I dislike this model, and prefer the semi-permanent health with regenerating shields on top... model.
Like last time, I'm playing the version from the Halo Collection on Steam. Like H:CE, this installment has original and remastered visuals. New cutscenes are lovingly rendered by Blur, and are stunning. I prefer watching the new cutscenes in playthroughs, but stick with the original graphics for gameplay. I'm aware of the Halo 2 PC port from 2007; the one that unnecessarily required Windows Vista. I remember when that came out, and it angered a bunch of people. Nowadays, not only is that version of Windows not supported, its predecessor (XP) and successor (7) aren't either, so it doesn't matter anymore. Wow, I'm an old man.
In the end, Halo 2 is a short and sweet sequel that's loaded with backstory that shows (instead of tells). I'm tempted to add Halo 2 to my all time favorite game list, just because I like the Arbiter's character arc so much. I'm looking forward to the next game in the series, but I'll probably play something else before I
worship the golden calf play Halo 3.