I'm guessing most of those games were using PC builds at max settings, especially Watch Dogs at E3, I would be surprised if Ubisoft had much time with PS4 and XB1 dev kits on final hardware. Yeah, I remember Killzone 2 was supposedly "in game footage" which was total BS, but probably got a few PS3 pre-orders Hell Wipeout HD is probably my favorite PS3 game still. It looks amazing to this day.
I think Halo 2 deserves an honourable mention. They actually had an entirely different city level for their technical demos than the one they actually went with. I heard that this was something to do with the fact that it pushed the limits of what the X-box could do. They wanted to wait 'til the next one, but they pushed the 360 back and Halo 2 forward, meaning they had to backscale it. https://www.youtube.com/watch?v=L_3tnAIgZ_4
Yeah, the missing Mombasa stage in Halo 2 was a major disappointment when the game actually came out. It looked absolutely fantastic on the "live gameplay" trailer at E3 2003. The scripted areas were impossible to manage on the old Xbox, so they had to basically spawn enemies along the way and delete areas he had already visited manually during the live gameplay, thus making it impossible to actually find a playable version of the level anywhere.