Well, I personally think HW will outsell KZ2. First of all, hype does not guarantee sales. KZ1 was hyped as "THE HALO KILLER!", and it ends up selling 0.75 million to a user base of about 80 million worldwide at the time. Fast forward 5 years and we're seeing plenty of hype again. Not Halo killer stuff but still very hyped nevertheless. Now people are saying it will outsell a game with the name Halo on it, on a user base of about 20 million. So either Halo Wars won't sell 1 million copies or Killzone 2 will sell about 5 million units.
Sure this game has great reviews, but again great reviews don't guarantee success either. Psychonauts is a great example of this. The polar opposite would be 50 Cent: Bulletproof, showing that even crappy games with just about no hype will sell over a million copies based on brand name (50 was probably the most popular rapper at the time). Halo Wars will most likely get great reviews, and thanks to it being a Halo game it will get great sales to boot.
