A game absolutely does not have to sell 2 million+ to get in to the greatest hits. Link me any evidence that suggests this is true, and I will link you 40 that say it isn't. You just flat out made this up. 

It is Sony's decision on whether or not a game is included in their greatest hits collection.  

Ohh well real numbers shown.

Well for it to be greatest hits it should have sold alot of copies. If in North america it sold nearly 1 million copies europe(were killzone is more popular) should have sold 1.25 copies. that adds to 2 million. But your right mitsuhide is incorrect look at it for your self but interestingly killzone made people buy a ps2...

http://www.gamespot.com/news/6074945.html

New numbers.

Resistance now has a 39% attach rate.

I'd say that sounds pretty bad but its probably typical of most launch titles.

Resistance has a higher attach rate than Halo 2 at the moment, but that's pretty common with launch games. Finland's best gaming magazine always has a one sentence recap after every review, and with Resistance it was "The one of the PS3 launch games that's worth buying." =P

I honestly don't see any PS3 games breaking 10 million this gen, and possibly only Halo 3 doing it with the Xbox 360.

I wasn't aware Halo 2 has such a small attach rate, that's odd, I thought it was considered the better of itself and its predicessor. Hmmmm...

I must have got an uninformed site when i typed into google "sales of killzone for PS2".

It did sell over 2million though it wasnt much of a flop just didnt play very well and the controls were weird.