I've never been a multiplayer guy.  I normally try it out after I beat SP and hardly ever go back.  I love to replay games and experience their story again.  Is the Killzone series good enough on SP to warrant the $40 purchase of the collection if I never plan on going online (I will try it out just not going to be sticking with it most likely).

I would say yes

Im also one of the few people who think Killzone 3 is a much better game than Killzone 2 however

Yes, it is. One of the better FPS series for story and game-play in my opinion. I'm also not much of a multiplayer person. It's the only FPS series I would pay full price for.

Personally speaking, I didn't like the single player campaign in either of them. To me, it doesn't do anything revolutionary and just seems like the same recycled formula as any other FPS game. Sure, the game looks amazing but it just doesn't do anything new or exciting for me.

KZ3 multiplayer is pretty good, though. I play that all the time and enjoy it quite alot. But since you're not buying this for the MP, then I'd have a hard time recommending to you.

Killzone 1 is quite good, KZ2 is very mediocre singleplayer-wise and I haven't played KZ3 but I heard that it's supposed to be better.

yes its worth it single player campains are grear

Yes. Get it.

played 2 and 3. They are good. Though I liked resistance FoM better

Wait a minute!

aaaahhhh fuck I voted because I thought you where talking about a Killer Instinct HD collection

Killzone actually has one of the more interesting and original settings, with the Helghast being off-shoots of humanity and all that. It's a very gritty and brutal world, which kind of draws you in. People have different tastes, but I honestly find that more compelling than aliens.

KZ3 is flat-out gorgeous. I loved the snow zones and the arctic platform levels so much. However, if I had to offer a criticism, it would be that a bit too much of it takes place in corridors and the vehicle sections can be forced and annoying. I also liked the MP a lot, despite not being a MP person, generally speaking.

I'm also very excited for KZ4, considering how KZ3 ended. There is so much potential there. I hope it goes in the direction that it seems to be heading. No spoilers, but I want things to turn from bad to worse.

Also, the upcoming Vita game lets you fight the ISA. That by itself makes me want it.