Halo has always been "the" game to me since the classic Halo 2. However, since the second Halo nothing has topped my shooter experience. Halo 3 and Halo Reach have come close and there's no question that Halo 4 comes damn close too.
Halo 4's campaign was great, I played through on Legendary. My only complaint was the Knight's and the lack of UNSC weapons. The new enemy introduced in this Halo was at first a cool addition until about half way through when I found myself annoyed and tired. These Knights are basically a bullet sponge that can be revived and teleport. So with a new enemy comes new weaponry and in Halo 4's campaign its everywhere and is basically your only choice in Legendary. The story was great though, you see a very personal side of the Chief and Cortana that you never have before.
The gameplay feels tight with no flaws, but there are some cracks in the presentation of the multiplayer. For one, the maps are not the greatest and there are only ten to play on. Also, the ranking is dull to say the least. I know its small things but I like to see an actual military rank when I play to get a feel of accomplishment when I rank up. I think the addition of custom classes was a great idea. Spartan Ops while short is a fun co-op play through.
343 have done a great job with the series and I think this game will only get better with time. I have a lot of trust in 343 and I know they listen to the community so I have a good feeling about the future of Halo.