I hate threads like this. No one game is the best online as everyone will have a differing opinion. The best technically maybe. Best overall though is just impossible to determine.

Well, the best online game on the ps3, in my opinion, is Call of Duty 4.

Mario Kart Wii , and Guitar hero World Tour!!

Left 4 Dead................. 2 months in and i'm still putting lots of hours in to this game, it's addicvite as hell.

best online ps3 game has to be MGO. It takes alot skill unlike the common Cod4/5 and in what other online game can you shoot, sneak, hide, surprise, chocke, grab, cqc etc etc. MGO is a masterpiece.

Th best online game will soon be Killzone 2!!

Indeed beta sounded pretty awesome...You can bet your points in clan matches...Otherwise pretty much like Cod 4.

in no particular order:

UT2004 (though I've always *hated* instagib.)
Tribes 2
Warhawk (I don't think this gets enough respect in the realm of online games. One of the most balanced games you will ever play.)
Aoe2
Left4dead (instant classic)
Counterstrike
Socom II
Ultima Online (in it's day was the best mmorpg ever)

I tend to disagree with Vlad's description of "skilled". While UT2004 is extremely skill based, it's skill based on an individual level more than it is on a team level. While there are team modes in ut2004, players dont really have any weaknesses if they are good. Other games like Team Fortress 2 or Warhawk, and especially Left 4 Dead also require a lot of skill to do well against organized skilled opponents, but being rambo in those games will get you killed over and over, regardless of how good you are as an individual player. That doesn't mean there is less skill required to play a team-oriented game, it means the skill goes beyond aiming accuracy, strafing ability, map memorization, and gun selection. It requires skill working as a team to win. Each class in Team Fortress 2 is gimped, each vehicle or soldier in Warhawk has limiting weaknesses, and the Left4Dead survivors are completely useless alone. Player skill is obviously very important, but team skill can be just as important, and just as hard to get right depending on the game.

Conflict: Denied Ops

Killzone 2 will be, but right now i think Resistance is verrrrrrrrrrrrrrry fun. I also really like the zombie mode in CoD5, only problem is they need more places. Metal Gear Solid 4 is the bestg single-player game ever (with-out a doubt), and is (im pretty sure) the PLAYSTAION 3's best exclusive. Little Big Planet looks fun (especially since theres no other game like it) but I havnt tried it yet.