I've just finished playing Killzone for the PS2 and it's a superb game- and it's only partly due to the fact that it's an enjoyable first person shooter. What really grabbed me about it was the design- it's simply superb, one of the best realised imaginary worlds I've ever encountered. A prime example of that it the very good weapons design. Bullpups are the name of the day with the good guys armed with assault rifles, sniper rifles and a neat suppressed PDW-type weapon all along the same configuration. Apparently one of the game designers likes to hang out in Nevada and shoot full auto weapons. It shows.
Anyway, here's the trailer for the follow up Playstation 3 Killzone. The story is basically this- fight off the bad guy (think futuristic Nazis) Helghast army. From the looks of this trailer, this game will be just as much fun as the first.