I think Killzone 2 will do better than R2. It'll more than likely hit a million worldwide within a few weeks to a month of month and do modest numbers over the summer.
I think you guys are making a stretch by using Uncharted as an example of a PS3 game that did well after starting off with low numbers. Uncharted saw a hefty portion of its sales through bundles. The only way this comparison will be relevant is if Killzone 2 is eventually bundled.