Yall are underestimating Resistance 3. The 1st Resistance sold 3.7 million at the beginning of PS3 generation with minimal user base (of course, it was the only decent FPS at that time), while Resistance 2 was a disappointment with its sales of 2.1 million and its reception. Killzone 2 sold 2.5 million. If Resistance 3 comes back strong, it can sell 3 million. I think Killzone 3 will most definitely sell 3 million and possibly 4 million.
So I think it'll be real close between R3 and Killzone 3.
We have no idea how Crysis 2 or Deus Ex or Rage (critics darling last year).