I think Desert Journey scaled the best out of all of them.
The two Act V cinematics, but especially Destruction's End, have a distinct checkboard pattern in the original videos that is not present in the other acts. I would guess this due to changes in how they compressed the videos in the expansion compared to the base game. Upscaling does not fix this issue, and as a result there are noticeable artifacts compared to earlier remastered cinematics.
Destruction's End scaled particularly poorly because of two main reasons: Tyrael has a ton of visual effects on him that limit the visual quality on his body and wings, and there's a lot of motion that caused a lot of compression artifacts in the original videos.
However, even the scenes that didn't benefit much from upscaling still benefit from the framerate increase.
Here are side-by-side comparisons for each cinematic:
- Act 1: The Sister's Lament
- Act 2: Desert Journey
- Act 3: Mephisto's Jungle
- Act 4 Intro: Enter Hell
- Act 4 Outro: Terror's End
- Act 5 Intro: Search For Baal
- Act 5 Outro: Destruction's End
Additional note, some of the videos are monetized because they were auto-claimed as belonging to Blizzard (which, to be fair, they do). So if you're seeing ads on them, that's why.