Halo Reach is a welcomed addition to the game franchise. Bungie has really delivered this time with just about everything you could want from a halo game.
Firstly the graphics received some tweaks, which I am not sure matters but at first glance the graphics seem much better than previous halo games. However they are really just re purposed, all of the weapons received major cosmetic upgrades as well as the armors and their permutations. This however came at the cost in detail to various bits of terrain and most noticeably vehicles, which look far less refined when compared to halo 3 / ODST.
There are some small additions though to the graphics engine and that is the number of particles that can be on screen, so that means lighting effects and explosions look very pretty. Also this allows more to be happening at a given time, you find that more characters can occupy the screen / level than previous halo games.
The immersion though gets inhibited by the AI. Bungie went through alot of trouble making the covenant act entirely believable and execute tactics with great judgement and cunning. You really feel like you are fighting an intelligent foe. The enemy AI might be the best thing about Halo Reach, but it too is impacted by the awful friendly AI. In fact the friendly AI is so horrible they often shoot you without abandon, or at nothing at all. They have horrible path finding, and their ability to pilot vehicles has been ruined in comparison to Halo 3.
The Single player campaign is the best since Halo Combat Evolved. It has references and scenery from what seems like all the other halo games. It plays how Bungie intended Halo 3 to be. The levels are spectacular and the map design is wonderful. Another big plus for the campaign is it is co-op and has a matchmaking playlist, which means you don't have to play with only friends. You can pair up with up to 3 other players and take on the campaign together.
The biggest disappointment about single player and the game difficulties is that after the Heroic difficulty the game doesn't change. All it does is raise enemy health and shields to the point that some enemies are near impossible to kill. There are some cases where you can spend all the ammo for both of your weapons AND use all four grenades and the enemy you are fighting won't die. This is no reflection of skill it is a cheap cop out in an attempt to increase difficulty. This is also very boring when you just sit there holding the trigger forever.
Halo Reach's saving grace is it's multiplayer. There is so much content for multiplayer that it would not be possible to cover it all. Just the sheer amount of content alone is worth a high score for this game. It delivers to the console unparalleled freedom in level editors/game editors/ content filters and search engines/ game types and much much more. The most noticeable change was the addition of armor abilities. Armor abilities are spread over a Battlefield load out style selection, where you select a set of weapons and a ability that goes with them. They add a whole new and different dynamic to how Halo is played. The weapons/ Armor abilities are balanced very well and make the game fun in the way that there is no one thing people can abuse in the game to get an unfair advantage. There is also a large number of unlocks for your character and community that give even more incentive to play and replay both single and multiplayer.
Another interesting addition is that assassinations are no longer just a quick melee, now you have the option of holding the melee button and performing a satisfying animated assassination. Though use caution because it is possible for a enemy teammate to see their friend in peril and come to their rescue and eliminate you.
Over all Halo Reach delivers an great experience, it just fell short of really being an excellent game due to a couple issues with by themselves are not horrible, but given the fact that they go hand in hand with one another, they do enough to hold back the game's true potential. It however a rewarding experience whether you are a casual halo fan or the most hardcore zealot enthusiast. There is immense replay value and lots of new things for halo that are sure to keep Reach going strong for a while to come.
+Good graphics (although mostly the same they were tweaked to give a noticeably different appearance)
+Scarily realistic enemy AI
+Great multiplayer game balance
+Loads of content
-Horrible friendly AI
-Legendary Mode does not progressively increase enemy AI as it did in other Halo games
-Cost of graphical tweaks was a reduction in vehicle detail / interaction