As I primarily play RPGs, controls are usually kept roughly the same and while I do appreciate updated graphics, I'm a modder so it's not a requirement. More important are bugfixes, primarily those that are at an engine level which are generally more difficult to fix with mods.
While a lot of people were disappointed by the limited upgrade to the graphics in the Mass Effect Legendary Edition, it was a great update for modders as the original games were 32-bit and easily could exceed the memory limit and crash. The update to 64-bit solved this issue and allows for more ambitious mods.
In recent times the update that I value the highest has been introduction of ray tracing or even full path tracing in older titles.