Why do older video games and movies worst audio then newer ones ?

That could be based on several different factors how old is the video game are you playing first of all because most video games now use a Blu-ray disc this holds about six times the information that a regular double CD holds a regular CD holtz about half of that which is about 600 to 700 megabytes then you go back to a Nintendo 64 the reason it was called a 64 is because it only ran on 64 megabytes an old-school Nintendo not the original but the older ones ran on 32 megabytes and the ones before that we're only 8 megabytesif you're playing like the original Zelda you're playing on a 32GB systemnow when you go to the modern Zelda it's being played on a Blu-ray disc which is approximately a thousand times more information this allows for full video and full audio in the video game.

They were top notch for the day but that day is long gone.

I guess there were limitations with sound production.
Hard enough to produce constantly moving and changing graphics, if speed and memory and graphics were already taking up huge chunks of computing space i imagine it was the thing easiest to compromise.

Google "FM synthesis". More generally though: transistor densities are the problem