KZ2 was best, spent hours on the multiplayer until Bad Company 2 came along. Has any other MP shooter done the assassination mission (target one specific player) or have placeable spawn points?
Killzones 3 and 4 came along just when the sprog meant gaming was off the menu for a while... Shadowfall's on my ps4 but I've never really felt i nclined to play it much.
3 was the one with all the 3D elements in the campaign cos sony had just launched 3D TVs - story ended with loads of green shit killing everyone on the Helghast planet. Snow levels.
Trivia. A friend from college got his first job working with Geurilla on KZ1. He's still working for them. Had no game experience - they recruited him because they wanted artists from other backgrounds and he was a stage designer for theatre. Crazy that this studio with so many inexperienced staff gets the job of making a Halo killer.
Still regret not making a better effort to get into Geurilla (I was young and very green), but by the time I got the opportunity, they'd changed ethos a bit and we're chasing people with more digital/ game design experience.