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.
The definitive evidence that video games turn people into mass murderers








