Thaurin
SasqWatch
Not if it was true HD - but it almost never is.
I think C&C - Tiberian Sun uses 720p cut-scenes. No idea about how compressed it is, but it sure looks pretty.
They do this because they're targeting machines with low specs, and they need the cutscenes to look right. They don't do it because the engine couldn't render it real-time on screen.
I assumed that they want to have the in-game and pre-rendered scenes look similar, but also want to have a few scenes that the engine *cannot* render. I mean, it's obvious in console exclusives like FFXIII that they don't really cater to the lowest specs... and the pre-rendered scenes look much more impressive, but the characters look very similar. I just bet that they could do even better these days with their rendering farms, though.
So, even if The Witcher 2 used recorded realtime rendering (which it doesn't) - it would still mean the engine is capable of doing what you're seeing.
Uncharted 1 & 2, as I said, also uses pre-rendered in-engine cut-scenes so that the game can load the next level without the player noticing it. Okay, so I'm talking about console games now, but those are the reasons why those pre-rendered cut-scenes look so much like the actual game.