I don't think sales necessarily always equal a better game but its quite clear the games are absolutely comparable.  They're sci-fi FPS first party games with a emphasis on both campaign and multiplayer.  It's quite clear that they're targetting a very similar audience and demographic so can and should be compared.  Sony must have tried to understand why Halo is a huge brand with the sales it obtains and the Killzone franchise isn't performing as well, it would be gross incompetence if they didn't themselves. 

When you compare how Killzone 2 did critically then look in comparison at COD and Halo sales something has gone very wrong.  I personally think its a combination of poor marketing, average first game in the series, control scheme thats not familiar enough to people and ultimately its on the wrong system with a smaller group of the demographic of users it targets. 

The question Seraphic_Sixaxis asked is perfectly valid and one that Sony must have asked too so don't be so harsh on him.  That being said there are too many Halo fanboys that use the comparison to somehow dismiss the quality of Killzone 2 so I can understand why you get tired of seeing the argument raised as it probably brings the same haters into discussions constantly. 

Perhaps Killzone 2 going platinum and marketed (possibly bundled) well around E3 with any potential announcement of a sequel will drive it up to near 4 million LTD which would then in my opinion be classed a real success given the investment and quality of the title.

in no way shape of form can you compare halo and killzone, 1st party fps titles are where the comparasions end. To compare a game they have to be the same, gameplay, target audience, multiplayer set up, etc. and killzone has nothing similar to halo.

Halo plays like a classic fps, weapons and perks are pick-ups, halo is accessible, it has vehicles, and much larger maps, weapons are futuristic (lazers, etc) characters are extremely unrealistic (20 foot high jumps, full health regen, take a lot to kill) enemies are clerly aliens, nothing is realistic, very bright vibrant, multiplayer isn't classed based, and there is no emphsis on teamwork, tactics, stragey, etc.

Now take killzone, dark gritty, not accessible, classed based, warzone last 3x alongf as a halo match, high emphsis on teamwork, strategy, tactics, realistic at it's core, no over the top aliens, weapons grounded in reality, gameplay realistic, no vehicles. 

the games are near polar opposites. you can argue what Sony wanted, but Guerrilla sure didn't have halo anywhere in their heads when developing killzone 2. Same however can't be said for resistance.

but mabey your right and mabey that's why killzone didn't do well, people were expecting sony's halo (literally) and got something totally different, and if that's the case then it just wasn't very fair for killzone 2 imo