Red dead is a great game, but is like Jules86 said to be honest. Personally i loved it though. Great graphics. Great story. And great online - the ability to create your own gang, or posse, and roam together to kill rival gangs was cool!!
I played it on the PS3 since I don't get time to play online very often. If you have XBox Live you may as well get it on at platform as I can see the online being much more fun on that.