@Ssliasil
Killzone 2 works at 30FPS but in some scenes its frame rate dips down quite a lot (at worst it goes down to 24 or 22), search the Digital Foundry articles for an accurate frame rate analysis covering most of the single player campaign.
The dips in frame rate are not evident to the eye, and maybe someone could think it's at 60FPS because of its really good object-based motion blur that smooths movements.
A bit like it happens in cinemas, where the images of a standard movie are only 24 per second, but the blur ties them together so that they appear much smoother than most 24FPS videogames.







