lol check the major league gaming site, gamebattles.com
top seven most popular arenas

call of duty 4 -xbox 360
gears of war2 -xbox 360
call of duty waw -xbox 360
halo3 -xbox 360
fifa 09 -xbox 360
rainbow6 -xbox 360
super smash bro -nintendo wii

says it all about which is the machine to get for online gaming experience
i also noticed when playing cod4 on my xbox and ps3 the xbox players were generally of a higher skill level lol