Overhyped, but still a great addition to the Halo series.
After the mediocre Halo 2, Halo 3 comes onto the Xbox 360 with some great new additions. Matchmaking now has a much better ranking system. Besides the number-ranked Team Slayer, Team Objective, Lone Wolves, etc, an overall military ranking is given ranging from recruit all the way to General. Winning games earns you experience, and your military ranking will never go down from a loss. Social matches don't have numbers, but wins still go towards your military ranking, and you can brings guests in too, adding to the fun in matchmaking. As you level up and accomplish tasks in campaign, you gain new customization options for your appearance. Bungie has removed the clan system, which isn't really a big deal considering how clans weren't really used in Halo 2.
Also new is Forge, which allows you to edit objects on built in maps to create new maps. However, forge can be irritating to use. The controls and gravity can sometimes be frustrating to work with, and when selecting objects they will occasionally bump and move other objects that you spent some time putting together. There is also a budget and limits on what you can place. This works if you decided to play Team Slayer or something similar on Forge with friends, but on many maps it can prevent you from getting truly creative with what you want.
A great new addition is the ability to playback previous matches and campaign levels. The theater is used to watch these games in a third person view (you can go to first person for the party leader) from any player in the games. So if you pulled off some crazy killing spree, you can show your friends. You can save clips, pictures, and entire matches through the theater.
Forge and theater combined with the file share make things even better. Each player has 6 slots (more if you want to buy them through the market place) to upload maps, game variants, videos, and pictures for anyone to enjoy. This essentially means if your friends like a map you created, then they can download it for use without needing you to come online. Although people can sometimes steal game and map variants, this is inevitable and not the fault of Bungie in the least.
New game types are also available, and more customization options are available for the old ones. Infection is now an actual gametype, meaning that unlike Halo 2 if you're killed you don't have to manually switch teams. Oddly, the infected can not be made to resemble Flood, something that would have been a cool feature (you can make them any color you want). Also new is VIP, which involves one member on each team being a target for the other that his teammates must protect. Territories has been improved to an offensive-defensive game, making it much more enjoyable.
Campaign mode is much better than the one in Halo 2. You only play as Master Chief, with a second player playing as the Arbiter and a third and fourth from Xbox Live being random Elites. Story mode is kind of short and can get boring (the eighth mission is just awful), but for the most part it's very fun and can be challenging, especially on legendary with skulls turned on, and the ending is much more satisfying than the previous game's.
Halo 3 doesn't add much to the gameplay, however. Players can now use equipment, although most of the equipment isn't effective for killing opponents in most cases. You'll usually find yourself still preferring to use weapons. A cool feature is the ability to rip of turrets and carry them around, and the camera changes to third person, and you can finally fly human aircraft in the form of the nearly unstoppable Hornet. The control scheme has been improved for the Xbox 360 controller, which is a good thing.
The graphics aren't very impressive for a 360 game, the levels are mostly made up of either hallways or open areas.
The final installment of the first Halo trilogy is no doubt an entertaining one. It's not perfect, or the best game out there like the hype made it same, but it's still one of the top games on the Xbox 360. Hopefully, Halo: Chronicles will be able to continue what has been a great series when it comes out in a few years and Bungie will continue making great games like this.