What do you need?
Game Center on iOS is supported on iPhone and iPod Touch running iOS 4.1 and on iPad running iOS 4.2 or later. The devices that can run Game Center are iPod Touch 2nd, 3rd and 4th generation; iPhone 3GS, 4 and 4S and all models of the iPad. There is no support for the iPhone 3G and the original iPhone. However, Game Center is unofficially available on the iPhone 3G via jailbreaking. Gameloft Live and Openfeint are other online gaming services. For installing Game Center on iPhone 3G, check this link.
NOTE: Proceed on your own risk.
What is Openfeint, Game Center, Gameloft Live, Origin and etc?
These are the names of different online multiplayer gaming services. Game Center is owned by Apple, Origin is owned by EA, Gameloft Live is owned by Gameloft and Openfeint is owned by
GREE. Game Center and Gameloft Live lets you play online multiplayer while Origin and Openfeint only support achievements ATM.
Which games are supported?
To check whether a game is supported on Game Center or not, open up 'App Store'. Browse to the respective game and check if it has the "Game Center" text and a logo beneath the game logo.
Here is a screenshot to help.
Almost all games of Gameloft are supported by Gameloft Live but not all games have Online multiplayer. You will have to check those games on the App Store yourself by reading their description.
Games supporting Openfeint have
this logo somewhere in their logo, although not all games have them. Here are some uncomplete lists of games supporting Openfeint;
link 1,
link 2,
link 3,
link 4 and
link 5. You can always ask in this thread.
Games supporting Origin are EA only games.
Do I need a paid subscription of any of these services to play online?
No, almost all of them are free with the inclusion of option iap (in-app purchases).
Is it worth it?
Yup, totally worth the hassle.
How do I signup for these services?
For Game Center, you need a working Apple id or you can make a new one.
For Gameloft Live, check
this and
this out. Simply, you have to make an account in any Gameloft game.
For Openfeint, when you play an Openfeint supported game, you get a guest account with a random username which you can customize later.
For Origin, just go
here.