Well, I played Resistance 2 and Killzone 2. Why would you spend your time with Resistance 2 if you can have a game like KZ2?
I mean, some people say bad things about the storytelling in KZ2 but I strongly disagree and I think it's an incredible FPS (and the storytelling isn't that bad, it's just complex). Resistance 2 is just a generic FPS IMO.
Maybe Killzone 2 killed the popularity that Resistance 2 could have.