Could you say best game of the year?
Campaign: Haven't finished it yet, but so far it is great! The story, the cut scenes, the graphics and the gameplay of the campaign is awesome. The best part is that each mission isn't the same. The environments look different in every level or mission. I mean you are fighting in a sandy area, then a dark night area, then space, and then in the covenant's ship. Some missions such as Tip of the Spear you are riding vehicles constantly and it is a blast especially if you are playing with other people. The space combat mission is a lot of the fun than I expected. It is also more challenging which is great. On the 7th mission so far and have been playing campaign on heroic difficulty. Can't wait to take on the legendary difficulty. Another great thing is you can do 4 player matchmaking campaign and 4 player splitscreen. Right now you cannot do campaign matchmaking due to Bungie not wanting to spoil anything for the people who want to beat it solo first. This is definitely the best campaign in the series.
Multiplayer: I am not going to say too much about this one only because there would be a lot to say. But all in all it is terrific. Still similar to the previous halos which ain't a bad thing, yet the new armor abilities make it a lot more funner. The assinations are a lot of fun also. I believe there are over 40 of them. But they never get old. There aren't too many game modes at the moment, but they are still terrific. Bungie will be releasing new ones soon. My only complaint is there are not too many maps and about 1/4 of them are from previous halos. But that is what forge world is for right?
Forge: Forge is a great tool and it has definitely improved from last year. It is quite big, forge world. I made a map with my brother and we were quite satisfied with our first map. But there is one problem. When Bungie demoed forge world it looked extremely easy to snap objects together. I somehow find difficulty in this process or maybe it is just because I do not know how to do it. So I used coordinates which is extremely easy and much more effective, but it takes a while longer. The new phased mode is great where you can not only place it where you want it, but place it through another object. I'm loving it so far.
Theater: Don't use this mode to much and haven't yet in Reach. But I have heard there are no parties allowed in theater which could be a bummer. But people are too busy playing multiplayer and campaign.
Firefight: It is similar to ODST obviously but seems a lot more fun to me especially since you can really go in depth in customizing it such as how good the aliens can hear you or see you. Pretty interesting stuff. Oh and there is also firefight matchmaking which is awesome.
Customization: Customization has improved greatly from halo 3. There are much more options such as visor color, firefight voice, and certain effects. There is also a lot more of armor to choose from and you unlock more armor as you rank up. But they certainly aren't cheap. There is a credits system involved, but it makes it funner. You can earn these credits in any game mode and also through Bungie's weekly and daily challenges.
Graphics: I actually really like the graphics in Reach. The armor looks more oldish and rusty which makes it cool. You can also use your armor in cut scenes or you will see it. There is one problem during the cut scenes which is a slight blur when motion is involved. But it really isn't a major problem, only a minor.
Sound: It's Marty, of course the music soundtrack is awesome!
Overall: Please go out and get this game, it will not dissapoint you. It is definitely worth the money and will be fun playing for many months. It will definitely be competing for game of the year with a few other games, well mainly Black Ops. But Red Dead Redemption and Fallout are also certainly in the competition. Halo deserves it so far only because of how much it improved.