Killzone was prerendered. Watch it again and notice how smoothly the "player" walks around. It's impossible to do that with the controller. You also notice that their is no varience in the frame rate. Even the fastest and most powerful computers will slowdown a little bit (maybe from 90 FPS to 50 FPS) when there are huge explosions going on.
The other thing I am sure is prerendered is the gas station explosion. Notice that both times they do it, when they go do the faraway shot (not the one from above) a door falls the exact same way in the exact same place both times, on the left side of the screen.
Maybe the PS3 is capable of those things, but I feel deceited