The beginning of the Killzone demo flying over the city was the only thing at the conference that blew me away. Knack didn't impress me too much personally and some of the other things that were shown weren't completely indicative of what we'll see in game.
The thing about Killzone, however, is that once the 30fps becomes apparent and the battle begins, that's where reality sets in for me. It looks good (particularly for a launch game that's not finished yet), but I steadfastly disagree with the "this is better than high-end PC" exclamations I've heard.
That said, I have little doubt that in a couple of years time, games on the PS4 such as Uncharted and God of War will be in a league of their own visually.







