No....Call of Duty 4 is still king, even over Halo 3 in my eyes (although I still like Halo 3 more than Killzone 2 as well, Killzone is still a great game, just not my style).

I never cared too much for the COD games(I liked them,just not obsessed).

Killzone I like,but again not insane for.The online is great,but I would like more variety in the mission objectives.

Overall,I feel Halo 2 is my favorite online shooter of all time,or maybe R6:Black Arrow.

For PS3 owners probably. But overall, it'll take another multiplat to dethrone CoD4.

COD4 is better than KZ as far as substance is concerned. KZ2 is better as far as graphics and realism is concerned.

If he's looking for a competitive shooter then just go to mlgpro.com and read up on the games they use on their circuit. If Killzone 2 can have as much competitive depth as Halo 3, COD 4 and GoW 2 and also have a massive fan base that creates a unique community for its users then ok. I haven't played Killzone 2 so I can't say but judging from the number of people that still play Halo 3 despite 'superior' games having been released I have my doubts.

edit:

Although I have to say Killzone 2's clan feature looks amazing and is something that should be implemented into every FPS.

Imma have to say they tied... and i still havent played WaW so i cant comment on that