In regards to Killzone 2 being a system seller, I have a little faith that it can be. Killzone 1 was downright terrible. But Killzone: Liberation on the PSP was actually a very well executed game. The media didn't find it remarkable, but it's a PSP fan favorite regardless (I know you Wii owners know what it feels like when the media doesn't appreciate your games). Based off that title and the huge budget for the new one, I think there's some chance that Killzone can be a system seller.
My Top 5:
Shadow of the Colossus, Metal Gear Solid 3, Shenmue, Skies of Arcadia, Chrono Trigger
My 2 nex-gen systems: PS3 
and Wii 
Prediction Aug '08: We see the PSP2 released fall '09. Graphically, it's basically the same as the current system. UMD drive ditched and replaced by 4-8gb on board flash memory. Other upgrades: 2nd analog nub, touchscreen, blutooth, motion sensor. Design: Flip-style or slider. Size: Think Iphone. Cost: $199. Will be profitable on day 1.
