I think the main thing, as others have noted, is that KZ2:
1 - is the second title in a franchise thought to be weak, it also didn't make its debut on PS3 so was easy in a sense to ignore if you were of the view from KZ that it wouldn't be good. Resistance, etc. started on the PS3
2 - it was perhaps too different with regards to controls and how easy it was to 'pick up and get into' online. I liked this, but clearly we are seeing that the big numbers are for casual titles - for example I see MW2 as a casual title. Fun, easy to play, easy to feel good in, allows for people to genuinely get good, but really the focus is on short, fast rounds in small maps.
3 - it is an FPS on a console who has a competitor where FPS sell better. In the end all the exclusive FPS are there to satisfy a need to have such titles, much as 360 has exclusive titles in genres that sell better on other consoles. As such it always had a glass ceiling.
Mostly due to 3 I have no doubt there will be KZ3. In some ways such titles (in terms of point 3) are loss leaders for Sony/MS, and aren't subject to normal sales expectations in terms of being profitable or receiving a sequel.
With KZ2, due to good reviews and solid sales, I think the groundwork is there for KZ3 to sell better. But unless they ease back a little on some of the unique aspects (hopefully not too much) then I think it may always been seen as the 'difficult' FPS to get into vs say Resistance or titles like CoD and BF.
Try to be reasonable... its easier than you think...
