JC2 is actually on sale for 7.50 at Greenmangaming right now. It's been cheaper and likely will hit cheap in the summer sale but if you're the impatient type, not a bad price.

my 2 cents:

I liked serious sam really a lot (even the slower earlier levels) It's a really good shooter that actually still feels like it's still fits in its own IP from years ago.

Bulletstorm was fun while it lasted BUT it felt so consolised. I don't really mind but it was a bit too much for this one. No jumping everything you do had a prompt. It just felt too limited for an old school shooter. It felt like everything around you you didn't have any impact on you at all. If people talk about consolised gameplay: this is it. But then again that does not need to be a huge negative. I had a lot of fun with it.

JC2 looks great and looks like a great deal of fun but i neven played it. The reason: i'm not really into open world games. Either i feel overwhelmed or it basic gameplay feels too gimped because of the open world (they can't control enemie behaviour or script stuff as much as in lineair, level based games). But if you love open world i think you will like this.

Just cause 2 if you like open world games and want to go anywhere you please. It is also fun but does get a bit repetitve

Seriuos Sam 3, I haven't finished it just yet but i am having alot of fun with it. Honestly, I haven't tried the other too games listed. I've played the first 2 games in the series and the latest, like the other two is alot of fun.

Just Cause 2 for sure! I didn't care for Bulletstorm that much, even though it looked good.