Well, we kicked off with an old Atari 2600 console in about... 1979. Err, not old at the TIME, of course...
You couldn't really quantify the difficulty of games at that time because they weren't sophisticated enough, though some tried harder than others.
Like I say, come the Spectrum/Commodare days, games of ridiculous hardness to i crease play length came. By the NES came onto the scene, gaming was entering a epriod of sophistication on all systems which led to be move up to 16 bit gaming which really established games as we know them today.