It's not like everyone has HD capture/recording equipment laying around.
I (and seemingly many of you) have already come across some HD videos or at least reasonably high-quality videos posted on this very issue. Now surely the people who made these videos should also have the equipment to take reasonably high-quality screenshots of the exact same objects from approximately the same angles in roughly the same conditions?
To increase the chances of replicating a good comparison, try it on objects that are less likely to change drastically in appearance; e.g. the character selection screen at the start of the game, objects in the menus, objects in areas/environments with consistent lighting and conditions, etc.
A video of a walk through the local brothel typically isn't a great comparison tool in cases such as these, unless the graphical differences are significant enough (and according to most posters it seems that the graphical differences are not significant enough to make them very noticeable with a lenient comparison video).
Also, keep in mind that YouTube normally lowers the image quality of uploaded videos. Try uploading screenshots or video slideshows where the image quality won't be compromised.