The original Killzone (PS2) was largely criticized for having several blatant flaws, such as serious AI issues among other glaring technical glitches. Hell, the entire game was smacked for its slightly repetitive gameplay. On the other hand, the game's unique storyline, noteworthy design and decent online experience helped improve the situation.
Due to its advantages, the franchise managed to garner a solid fan base, which is why the game's approaching full-on sequel also generated much attention during the E3 2007. Killzone 2 is, at present, a PS3 exclusive and is scheduled to ship some time during 2008.