For some reason there's a lot of controversy surrounding the Halo franchise; people seem to either love the games, or they hate them. There is very little middle ground. I'm no exception.
Halo 3 is, hands down, the best online multiplayer FPS game on any console to date. There are many areas where Halo 3 is simply superior to other games in its multiplayer offerings:
1) Matchmaking. The matchmaking/lobby system is something that started with Halo 2 and Bungie has continued to evolve it into what it is today in Halo 3. The ability to enter different matchmaking playlists with or without friends is something that is only now beginning to be replicated by other games (Call of Duty 4 comes to mind) although none of them are yet able to do it quite as effectively as Halo 3 does. The numerous tweakable settings, charts that show your skill relative to other players and details regarding the number of people playing in each playlist are all icing on the cake. Add to that the new Veto system and you have an obvious winner. Nobody does matchmaking better.
2) Video & Screenshots. It's just plain cool to be able to go back and watch that clutch cross-map sticky grenade that saved your flag from being captured at the last second. Add the ability to upload and share your films with friends (or enemies) and even detach and rotate the camera, or take screenshots, and you're golden. Bungie outdid themselves on this one.
3) Competitive play. Sure, there are a lot of other great FPS games out there. Call of Duty 4 is particularly popular right now. Resistance is a popular option on the Playstation 3. They're great games, no doubt. But none of them have the competitive aspect down quite as well as Halo 3 does. Halo 3 does a great job of matching you against players with a similar skill set (granted, it does take a few matches until your true 'rank' is established) and encourages tight, close games. It requires team work, a multitude of skills, great hand-eye coordination, and precise-yet-lightning-fast reflexes to be truly competitive and successful at this game. It's no wonder it's the game of choice of Major League Gaming, the world's premier elite gaming league.
4) Forge. The ability to customize most aspects of the multiplayer maps allows for seemingly unending creativity and a multitude of new online gaming scenarios.
5) Number of unique players. At any given time in any given 24 hour period, you can expect hundreds of thousands of people to be online playing Halo 3 - there will be no shortage of new and unique competition to play against.
The single player aspect of the game is also great, although I won't go on a limb to call it an amazing, unforgettable experience. If you're a Halo fan, you'll likely be interested in seeing how this arc of the Halo story ends. It's far from disappointing, it just isn't anything mind-blowing, which many were expecting.
The graphics, in particular the HDR lighting, are exceptionally impressive. Some might complain about the bright colour palette because it isn't at all "realistic". To them, I say, "It's a video game!" Again, just to make it clear, the lighting is fantastic!
There is much more to praise about this great game, but for now I'm going to leave it at that because I have to get back to playing!