Why would you compare these two,yes i have played both and they are on their own leagues. And you know what,no online multiplayer has ever equaled the success the halo3 unless gears came.Even now i still enjoy playing halo3 online and its simply awesome.You can go on playing social slayer for ever and its super solid. Resistance 2 had some decent multiplayer but i was not impressed with the level of immersion that games like kill zone 2 gave me online.
My latest games in the line up is battle field bad company on the ps3,i missed this game when it came up and was lying untouched and now is the time for me to complete the single player and the level of detail in the game is awesome!!