The best Halo there is.
Story starts in the same place where Halo 2 ended. It goes on from there and wraps it all up giving a nice feel of closure in the end. This also means that you pretty much need to play the previous two games first in order to enjoy the story of the third.
Graphics are now better than ever before, but still this is not the best thing that Xbox360 has to offer. Luckily the use of bright colors makes the world feel richer. There is very little loading times so it is very much one big seamless experience from beginning to end. Cutscenes are, for some reason, somewhat ugly comparing to Gears of War for example. Sound effects are familiar and the voice work is great, but the actual effects fail to create that kind of rich and full environment like they do in Doom 3 or Quake 4. All in all in terms of audiovisual presentation Halo 3 is good, but not great.
Gameplay is just as good as ever floating smoothly every step of the way. There are a few control options to choose from, but still it would have been nice to be able to adjust them freely. Level design is much better than in the previous games and there are many missions placed in outdoor environments. This gives some battles an open-ended feel to them. The AI of the enemies is good making the battles interesting for multiple playthroughs. Unfortunately the same can not be said about your allies: Arbiter does some stupid things in a steady pace when he is controlled by the AI.
For some reason there are no subtitles outside cutscenes, which means that usually the comments from your brothers in arms and especially Cortana are not very understandable.
Multiplayer mode is the best thing in Halo 3. There is a campaign co-op mode for up to 4 people and tons of different other multiplayer options to choose from. Almost everything you can think of is here and the statistics are extensive. Only problem is that the limit is 16 players, which is beginning to feel a little old.
Halo 3 is here and it is your duty as a player to finish the fight.