I'm not gonna vote, as I haven't played Halo 4. The screenshots were incredible but that's not really a reliable method to judge with.
To be honest, though, sci-fi games like Halo and Killzone are much easier to make visually stunning, as you're dealing with alien worlds and details you can create as you like. Something like The Last of Us, with all its emphasis on people and a familiar-yet-unfamiliar world, might not look as incredible, though to me it's actually more impressive.
That being said, the most amazing visuals I've personally seen this generation were from the artic missions in Killzone 3. Absolutely incredible, especially those gigantic waves rolling under you.
Crysis graphics (on consoles) I'm not a fan of. They feel really flat to me while I'm playing.
