(2) Halo 3
Of course this list would not be anywhere near complete without HALO somewhere on it. Online play in the Halo series is probably one of the most popular of any console game out there; Halo 2 is practically what defined the original XBOX Live experience.
Halo 3, keeps the online mode going strong. With tons of downloadable content and a huge online community, which is still growing, the Live experience for this game will probably never run out. Players everywhere know what Halo is, meaning you truly are playing opponents globally when you hop online. The game can be described rightfully as "one of the most online multi-player gaming experiences ever conceived".
Players can traditionally play in casual matches or more competitive ranked matches which is actually kept track of; ranks and scores can then be checked on the official Bungie website. Leaderboards are also available to browse on the actual console as well. Many returning game modes from Halo 2 keep it going strong like Juggernaut, King of the Hill, or an Oddball type game where players must hold a skull for the longest time. Complete customization of the included game modes and levels however provide almost an endless possibility of online gameplay. Players can even come up with their own game type such as the newly created Infection, where one team is zombies and the others runs around with a limited supply of ammo fighting to stay "Human" as long as possible. Infection was actually created by the community in Halo 2 and become very popular.
Players can also unlock easter eggs and achievements which allow different versions of armor to customize their online avatar with. Weapons and objects in levels can also be changed completely through a game mode called "Forge" which can also be played online with others for those who just want to run around the level and fool around.
Halo is one of the greatest console series of all time; Halo 3 will surely not disappoint and the online experience is so great that it will still be around for years to come just like Halo 2 was.