In their time working with Sony, Guerrilla have brought two iconic exclusive franchises to Playstation systems; Killzone, and Horizon.

If we take each series in their entirety (so including "side" games like Killzone Mercenary and Liberation, LEGO Horizon Adventures, Call of the Mountain, etc) which do you consider to be the better series, and why?

I would like a new killzone, with a good multiplayer and a good campaign, killzone 3 was a lot of fun.

Killzone for me because I don't care about story or anything, I just want to shoot at stuff. =P

Never played Killzone, so Horizon by default.
Would be Horizon anyway as I'm not much into shooters, so even if it is great it's still a shooter.

I've only played Killzone 2 & 4, but I prefer Horizon by a wide margin. Even though they still have a lot of the same problems other open-world games have (e.g., repetitive copy-and-paste checklist objectives, too much time spent just on traversal), they bring enough to the table to more than make up for it. The combat, especially against the machines, is fun, the art style is great, the world/setting is amazing, and I love the story and characters.

Horizon is much much better

Both are mid.

Ive only played Killzone 2 and its was very mid, I find Horizon to be vastly better.

I really enjoyed Killzone 3 because it had campaign couch co-op so im a sucker for that.

Overall, I'd probably choose Horizon as I enjoy the environment and gameplay better. But I would love a new Killzone!

With a bit of experience from the first two Killzone games and all of Horizon: Zero Dawn, Horizon takes the win easily. Killzones looks bland, feels mediocre, simply isn't all that fun, and I don't like console shooters in general, whereas Horizon plays pretty well and actually has interesting lore/story. If the other Killzone games greatly improved the series or Forbidden West did something really, really bad for the series, I doubt my opinion can really change. Aside from the lore, I'm not even a huge Horizon fan, but at least Zero Dawn is a pretty good open world game.

Of course this is based on my limited experience and my bias against console shooters, but that's my two cents anyway.