Single player starts promising.
Its not a linear shooter that tells you what to do and how to do, thats sounds good, but it really isn't.
The second level is very good in my opinion, because it has good level design, so their open approach works here. But later the level design gets much worse and the freedom the game gives you just makes it frustrating because you don't know what to do and where to go.
There are a few good sections in single player, but overall its pretty bad and boring. Story is lame, characters are bland, pacing is horrible...
Multiplayer was shit right after launch, mainly because many people played it and didn't know what to do.
Nowadays its pretty fun, because Guerilla refined it and people know what to do by now.
I had to choose between COD MP and Killzone MP I'd go with Killzone.
When I bought the game with my Ps4 at launch the graphics were stunning in my opinion. Today I feel like the graphics are pretty flawed. Image Quality in MP is bad, in singleplayer its better but not as good as in Infamous.
Overall the game feels very rushed in every way, but they put some work into MP after launch so at least that part is good by now.