@Arcturus I would give Killzone 3, a 2 star as well.
I read some comments on the ps3trophies.org and this guys comments mirror my own.
"Gave this a 4. The trophies and actual difficulty of Killzone 3 (KZ3) is much easier than Killzone 2 (KZ2). The online trophies are easily obtainable with the exception of "Now you see me". Elite difficulty in KZ3 is easier & beatable in 6-7 hours mainly because you can be revived unlike KZ2.
Despite Elite difficulty being toned down for the avg gamer, there are a few rough spots in Elite Difficulty where you don't have a person to revive you and the enemies seem to have infinite spawn unless you inch your way forward."
The guy also talks about the trophies "Mopping up" and "Completionist" giving him some trouble. I also had a difficult time getting "Mopping up" to pop and "Completionist" took me a bunch of restarts as well.
For someone who plays a lot of shooters like myself, Elite was pretty easy. But I still took my time clearing out areas before proceeding. And for comparison I'll say Killzone 2 was also pretty easy on Elite for me too (I'd say 2-star especially compared to COD: World at War, a 3-star)... It was pretty easy all the way up until the end with the Radec fight. But the Radec fight I didn't use any knife tricks or glitches to beat him. So it took me approximately 5 hours to get to the final chapter of the game on Elite and then I spent another 5-6 hours just trying to clear that last chapter and finally beat Radec. Nothing as frustrating as that in Killzone 2, that's for sure.
Of course the online trophies and top 1% pushed Killzone 2 to a 4 star. For me I've always felt the 4 star ranking was very accurate since I had to get into the top 800 rankings when I attempted the top 1% valor medal much later on. And over 40 hours of online that week still only had me sitting in the high 600's. However if I did that trophy week 1, I would feel differently. Week 1, I made it in the top 5% without even trying and I only played the online that week for less than 4 hours. If I put in another 4 hours I bet I would have easily made top 1%.