Which online PS3 shooters remain the most active?

I have only been a PS3 owner for the last two months, until then I played games on my Mac, I'm not a hard-core multiplayer gamer, but I would like to try out something like Battlefield for Call of Duty. My question is, which game would be best best to spend money on in terms of online play and pure enjoyment?

Call of Duty Advanced Warfare, Killzone 3, Battlefield Hardline, Black Ops 2, Modern Warfare 3.....those are my top 5 :)

@cbasson1996: All those still have plenty of online activity?

Last time I went online was 2012, but too be curious, I just loaded up battlefield 3 and got a game no problem. So I just checked World at War and saw it has 1,000 players, checked mw2 and that was dead. Cod4mw, I got a game easy but it was hacked.

I think there will be plenty of players in the newer games. Like those mentioned above

Just checked out black ops. 20, 000 players were online and a lots of new players.

Just don´t log into COD4/MW1 multi, it´s full of hackers. Most of all the rest of the shooters are fine and have plenty action, while you are at it download Killzone 3 Multiplayer trial version, it´s free and it´s a lot of fun.

@viciousinjun: Yeah definitely...but I think Killzone 3 will be the best pick out of all those games