I play all those games Max with my 4850,
All my youtube vids are of me playing/demoing games, all run at max, 1080p.
And just the other day i put up a Fallout 3 Vid to
http://www.youtube.com/user/sniperviper21
some videos may skip a bit, but thats due to FRAPS being shitting (the program i use to record with )