Another huge step forward was the save game.
So trivial now, yet before local storage you either start from scratch each time or had level codes to skip ahead. I don't remember any games on MSX where you could save the game, always restart from the beginning, same on C64.
The first save game was in the 80's already, yet it didn't become standard until much later. Save games have definitely altered the way games are made, for the better and the worse. Focus has shifted to drawing out the game length with tons of padding instead of concentrating on the high score beating formula.
Even PC games didn't really save anything at the start. Many games were of course ported from arcade and consoles but also many made for PC games didn't bother with save states. Then stuff like Sim City and Civilization came around thanks to the power of save games! (Now where did I leave my level codes for Lemmings :p)