I know the game only came out a year ago, but it's a question I would still like to ask Halo fans. Before it's release, Bungie were hyping it up as the best Halo game and they would send their last game in their beloved (and often despised) franchise with a bang.
From a multi-player standpoint, I definitely think it's the best in the series despite the godawful maps that came with the game and armor lock. Definitely one of the most enjoyable and balanced online multi-player shooters of this generation.
But from a campaign standpoint, I thought it was the weakest or second weakest in the series next to ODST. One of the problems I had was the lack of epic set-pieces, and Bungie touted that the campaign will hold 40 to 60 A.I. on screen at once. But this is complete farce, as the game only had SLIGHTLY more enemies on screen than prior games, but not a single battle made me feel I was part of a war and there weren't any memorable set-pieces. Also, I found the story to be forgettable. A lot of people found the characters to be memorable, but I didn't give a shit for them. Kat and Jorge hinted character development, but they died off WAY too quickly to care. The story only really consisted of completing contrived errands for the UNSC, and the story didn't pick up until the last third act of the game. I will say that the ending was creative and emotionally engaging, but that's the best compliment I can give it. I don't think the campaign is bad, it's good but could've been better and the Vidoc hyped it up way too much. I will say that the enemy A.I. is very impressive; especially on Legendary where it's on par F.E.A.R.'s A.I.