SOCOM 2, of course. This is the flagship series of PS2 online. I also recommend Killzone, if you like your guns loud and explosive. If you're looking for a good online fighting game, check out Mortal Kombat Deceptions. It surprising plays smoothly online with assuming you and your opponent has a decent connection. TimeSplitters 3 is looking good, as is the new Champions of Everquest game, for the action adventure genre. Also, if you don't mind putting in a little work, you'll be able to play GT4 online using some LAN tunneling software (X-Link Kai). So, all hope is not lost. For the mean time, check out Burnout 3 and the Need For Speed Underground games. Also, if you don't already have a set, look into picking up a headset, especially for the team oriented shooting games. It adds a lot more to the experience.