Or just bombard it with those crusiers they have....

I am not sure, Helghast is a rubbish planet, though if you want backstory head over to the Killzone website, there is a ton of content there

I don't get it. Its an impressive intro and a cool video...but this does not game look better than Crysis.

Taking the game engine and making a video out of it, usully means boosting textures and detail as much as you want. Thats not what the in game looks like...

I don't know the full story of Killzone: Liberation, but I've heard that the Helghast stole nukes before they retreated.

In fact, Viscari alludes to this in his speech,

"By seizing the weapons they thought they could turn against us"

Indeed, it's not like anyone would want to live on that place, and it's a war of power... what better way to say you have power then to turn their whole planet into a parking lot, am I right|? 

Really the reason they don't is because that would be a short FPS :P opening intro of the game just one giant nuke to wipe out most of the planet.

Maby crysis is SICK and all but maby people get bored :/ I dunno i was just thinking a while ago what if crysis is kick ass in gfx ( which it probably is ) but the environment ..maby is uh what am i looking for.. same? or something I DUNNO DONT HIT ME! just saying maby its not impressive unless u go close and think about it? XD i dunno nvm! XD

Reading the back story though, I believe that Helghan has some valuable things that can be mined. It's just trying to live there is the problem.

I think you activate a nuke in this game. Not really sure though.

Alright now, who hijacked Selnor's account? Be honest.

GG has stated that there are NO CG cutscenes in the final build. So if this is indeed the final game's opening it is rendered in real time. That actually is not that far fetched. I think the real reason some think it is CG is because of the animation. They used the in game models but reworked them with more refined animation for the cutscenes.

Its kind of how MGS4 was. All of it was in game but when a cutscene was happening there were more refined animations.

Selnor? Are you Drunk xD