depends on what system we are talking about.....i only have crysis 2 for ps3
if you are looking for a pc shooter that most people (on steam anyways) are going to have, tf2 is the way to go.....
Ill look into tf2, there does seem to be some interest in this, Ill sit down and come up with a date/time for the tourney as well as some official rules. If its popular enough I'll run a weekly tourney