VideoGame Once again, great game, not so great story, awful ending
I don't really need to write much about the gameplay, it's classic Halo and if you don't know what that involves then you're probably not the person this review is aimed at. There are some interesting additions, the biggest of which are AI teammates. Their usefulness can be questionable at times but on the whole they're a nice addition, especially as they give you a chance to get back in the game if you get taken down.
As for the story... well did you see that epic advertising campaign? The one where Master Chief and Locke have each other at their mercy? The one where it looks like the end of the world is neigh? The one where each character delivers an epic speech while preparing to deliver the coup de grace (in Master Chief's case, possibly aimed at himself rather than Locke)? Yeah, none of that happens in the actual game. They have a bit of a fist fight half way through, then they're pretty much on the same side. The MC/Locke switching is not nearly as effective as the MC/Arbiter switching in Halo 2 because the story just doesn't feel like it's working like it did in Halo 2. The Arbiter was on a journey as a character. Locke was just chasing a goal.
Cortana turning bad, I don't have a problem with. But I don't think it was done very well. MC has a relationship with Cortana unlike any relationship he has with anyone else, so why not show us what happens when that relationship is put under strain? There was a huge opportunity here to flesh out MC's character (something that 343 have obviously been trying to do since Halo 4 by giving him a lot more dialogue than in previous games), but it was an opportunity completely missed. How does somebody cope when someone they were that close to turns into a monster? What emotional impact does that have on you? Nope, none of that was touched on in the game.
And you thought Halo 2 had a bad ending? This game doesn't have an ending at all. The story doesn't resolve, it just stops. I mean, seriously. What reason have you given me to play Halo 6, from a story point of view?
Ever since the Covenant arc wrapped up, Halo has really struggled to deliver a compelling story. 343 really need to get this sorted, because while the gameplay is still as great as ever, it will grow stale eventually, and then you'll need to spin a good yarn to keep people coming back.
VideoGame Game Good; Story Bad
As far as the gameplay goes, I'm pretty satisfied. There are a few flaws and hiccups, of course, but the focus on this review is going to be the story itself.
First, the advertising campaign you saw? The one which made this seem like it'd be one of the most original and unique stories in the franchise, that promised mysteries to be solved and provoked your interest in "The Greatest Hunt in Gaming History"? It's all bullshit. There's no mystery. The "mystery" is solved by the second level. The "hunt" ends on the fifth (of 15). It's about as close to false advertising as you can get without being punished for it.
Second, the guy who wrote this, Brian Reed, possesses the dubious honor of writing both Spartan Ops and Halo: Escalation 8-10, both of which proved divisive at best. Recall in the latter when Black Team (a Spartan-II squad of four) was killed off in a fight off-screen to show off how dangerous the Didact was? It seems The Worf Effect is Reed's go-to cliche, because by the end of the first level, he has Jul 'Mdama whacked with little effort in a cutscene to show how dangerous and ''skilled' Locke is. Not even a bossfight for the Covenant Supreme Leader? Warden Eternal gets his bossfights. They even added Jul as a bossfight in Warzone. Why was it so hard here?
The biggest issue, of course, is Cortana (Spoiler ahead, of course). Now, for anyone not in-the-know on the EU, there actually is an established precedent for her behavior, one which ties her in not just with the Didact in Halo 4, but even other AI going nuts. In short, this is never touched upon. An exciting Myth Arc potentially established by the Forerunner novels has been hinted at nowhere whatsoever in the last two games, despite ample opportunity. Cortana's behavior, as it stands, seems completely out-of-character with no hint at an explanation otherwise. If there were, one might say "Wtf Cortana is bad now?! Hm, there might be more to this... I'll have to get Halo 6 to find out..." As it is, it's just a random Face–Heel Turn, and if it is explained in Halo 6, I can imagine overwhelming accusations of it being a cop-out designed to justify a bad decision in Halo 5.
Finally, there's the sense at the end of the game that you didn't really do anything. Cortana's plan is now underway and your involvement meant nothing to stop it. For all intents and purposes, it's Filler.
In summary, Good:
Bad: