Not needing months? Ive been stuck and struggeled for ages completing point and click adventures on Amiga over the years xD Also tons of RPGs from Ultima to the eye of the beholder have eaten big chunks of my life

Then we have management games that stretch on forever and heck Civilization on Amiga has absorbed a fair hundreds of hours gameplay. Dont get me started on the Elite games, jesus they can be played forever. Even Speris the legacy has eaten tons of hours and I havn't completed that one yet.
So yeah many games even of old can suck much time, same of todays games, there are plenty of few hours to complete single player games and tons of hour eating games like the elder scrolls/fallout series etc.
All about what genre you pick, old or new both have short and long games and many games can be short or long depending on your playstyle.
Amiga ain't all short platformers and racers you know.
Why limit yourself to only playing modern games or Amiga games? There are tons of incrediable games on so many systems from all eras!